The Average Approach
An example for this is Diablo, DnD, really almost every Action RPG out there, often strategy games too; as they all randomize weapon damage. Why is this acceptable? Simply because you use your weapon so often that it averages because of the sheer number of rolls.
It also makes the player think, do I want to do 2-7 damage per hit, or rather 1-8?

What you're basically saying is that it's okay because it's not really luck based. It's only an illusion. I might say this variable damage makes sense from a physical standpoint. additionaly if you're gonna show dmg numbers (which I dislike), you don't want to show the same number over and over again.

This, and critical hits makes the total damage unpredictable i the next few strikes. If only a few blows are required to take down a foe, then the chance of a sudden dmg spike will have a great advantage in killing foes in a holy trinity system. Healers will have a much harder time dealing with such unpredictable encounters, making the job require more skill. You might wanna sacrifice some average dmg in return for better random temporary spike dmg, making the optimal build more complex (isn't that what you want?).
The possibility of chance is not equivalent to less skill.

[indent=3]
Imagine finally getting the atom bomb in an RTS, after being almost overrun since you had to invest all your ressources into this, and then *Poof* nothing happens. Why? The superweapon does 200-9999 damage, and you just happened to roll low. Because of luck, you lost the game.

There's a difference between random dmg in something that takes lots of investment in a long game. In a rpg pvp match you usually respawn quite quickly so these are very different scenarios. There's also a massive difference between 200-9999 dmg and 5000-9999 dmg. The first has a very extreme dmg difference, while in the latter scenario it might be a devastating hit, or it might be a very devastating hit. A 10k hit might give you a win, while a 6k hit might prolong the fight.

Tohe alternative route
This is something that I have hardly seen in games. It basically says that luck depends on the outcome of the mission, but you don't FAIL. It means that the story goes in a different direction, or that you get different missions. This could be used for interesting effect, but it can frustrate the player, since he might not be able to see the story go in a different way when he replays the game.
A possibility to avoid this would be to program the game to automatically have it work out the other way when you replay the game. Say the game notes if you finished with version A, so the next time you will always get B.

So you dislike luck in combat, but you'd like it in story progression, instead of being dependent on dialouge choices?

To repeat my questions from the beginning: What purpose does luck serve in your games? Is it a part of your game at all? Should it be?

Specifically in a rts, luck makes everything more complicated. You don't know the exact outcomes of a given action. In other words it might require more skill, because you have to make strategic decisions based on uncertainties. If the utcome of a long match depends on one single event which is essentially a dice roll (200-9999dmg), then it's the bad form of luck. However a very similar scenario is where building of a titan means instawin, and so it becomes and arms race to build one first. The latter is not based on chance, yet it's similar and not much better.

The purpose of luck in a game is to prevent easily solved game situations. Take any RPG. If there was no damage rolls, you could calculate the number of hits required to kill your target, then compare than to the number of hits he needs to kill you. If you can kill him before, you always win. Luck will come into play by changing the battle flow at some key points. A lucky critical/evade will turn the situation around and change the battle flow, forcing you to change your strategy or lose what was once a sure win. Luck eventually evens out, so you still have a higher win%, but now you get to do something instead of watching pretty animations until you win. In this case, luck adds to the gameplay by creating risk/reward situations.

Luck can be a detriment when it affects the outcome of a situation in a dramatic way. For example, in League of Legends, Gangplank could land a ranged skill with a 4% critical chance. If it was a critical, it would take out close to half hp of the enemy champion, ensuring him lane dominance through luck rather than skillful play.

Games which have a lot of player decisions generally do not benefit from luck. Shooters and the like are such games. There are so many things the player can do in any given situation that the battle cannot be solved. This means luck isn't needed to break determinism. When the player has a limited set of options and few decisions to take, then luck is necessary. However, it needs to be dosed appropriately or it will either have no effect or completely determine the outcome. That 200-9999dmg nuke is a good example of a bad luck-based mechanism. You win or lose based on a dice roll rather than gain a small advantage/disadvantage.

When I first opened up this thread I was under the impression you would be discussing something akin to a beneficial ability, choosable talent or passive bonus the player could have. And while I completely get that you were in fact simply discussing what I would think of as simple randomness, I think it would serve the discussion if in fact that WAS one of the applications of "luck" you meant to discuss. Consider...

You've got an action rpg. Each player has the usual race/class possibilities, but they also each get to pick one special ability unique to their character which is not based on anything other than personal choice (i.e., any class/race combo could potentially have it). Call it their "talent".

Player A picks as his talent an ability which increases all damage from weapons by 10%.

Player B picks as his talent a dodging ability which reduces enemy chance to hit by 10%.

Player C picks as his talent...Luck.

But what does it DO? That's the cool part. Any time the game makes a roll which concerns the player it fudges it in his favor by X amount. The X would have to be balanced very carefully (obviously) but for ease of discussion let's just go with 3%.

Player C attacks Player A. Player C gets 3% added to his chance to hit Player A, and gets 3% added to his weapon's damage.

Player C attacks Player B, with only a -7% chance to hit.

Player A attacks Player C but only gets +7% damage.

Player C's chances to find loot, and amounts of general loot found (e.g., gold coins) is increased by 3%.

Player C's chance to critically hit is increased by 3% AND...anybody trying to hit C has their chance to critically hit reduced by 3%.

Etc., etc. You get the idea.

Now to me that is a cool way to implement "luck" in any game which incorporates RNG.

Take care!

Luck is a great companion to FPS games. Accuracy is the most prominent luck mechanism that works and no-one objects to it, because it is realistic, to some degree -- you shoot bullets, sometimes bullets miss the target, sometimes you cna land a headshot with a high enough chance to hit the spot you're aiming at.

Luck is applicable where the player thinks it would be realistic, or enchances the fun. In the Diablo example, it is logical a character might take a stronger or weaker swing at an enemy -- the numbers are arbitrary anyway. In the nuke example, if the rest of the game would be kept in a solid, consequent manner (normal weapons have steady, but low dmg, nukes have variable but potentially high dmg), having a weapon that deals nothing-to-overkill might be a good design decision. Everything depends too much on the rest of the game, so dissecting a specific mechanic put in a generic setting doesn't make sense. Take Diablo II's Sorc as an example -- Lightning spells had a great capacity to deal tons of damage to lots of enemies, or just tease them with a refreshing jolt of energy. Some of those spells cost a lot, so it was up to the player to "feel lucky" and create a thunder mage.

IMO, the wilder the difference between highest and lowest outcome, the more people can invest themselves in a certain mechanic -- be it hardcoded luck such as critical hits/damage variation or real world luck, such as launching a rocket and someone running into its path unintentionally. On this note, friendly fire is a great thing to dissect -- in a firefight, you have a chance to hit your allies if you're not carefull. It is not in any way luck dependent on the game code, but on the players themselves (save for the accuracy example in FPS games).

It's late (or early rather), so I may have missed it, but I wanted to mention a point about critical hits. Sure, this is a luck factor, but one point about them is to simulate actually getting a really good hit. In a real-life scenario, you won't always have openings to strike at to deal a stronger blow, and this seems to translate over.

Luck does not and cannot exist truly in a video game, and if it did, it would be a pretty rubbish component. The best thing is the ILLUSION of luck. The illusion of luck enables the creator to control what happens precisely, but the player feels they are on a lucky spree. This is the best and most exhilarating type of gameplay. For example, if you are playing an RTS, and you were dependent on random numbers or true "luck" you might end up with all of the resources on someone else's side of the map, and they would win and it would be no fun. But say you are playing a shooter like Team Fortress and you shoot someone and you are not aiming directly at them, but you hit them. This makes you feel lucky and further exhilarates the process of playing the game.

Luck should never be a deciding factor towards the win condition but should increase the potential of the win condition and a player should always be able to choose their bet in a situation that invovles luck. As MrJoshL pointed out, controlling luck can be a good tool but nothing takes a player out of a game more then becoming suspicious of the game's "control" over them. The player should always be the one in control, the design should inspire the player to want to test their luck, skill, timing, etc.

Don't forget that "luck", or what I would call randomness/RNG has different ramifications for different genres. Kind've like MrJoshL and Mratthew illustrated.

But I would think the more a genre tended towards an FPS the less RNG should play a part. Conversely the more the genre tended towards an RPG the *more* RNG should play a part. I mean the very nature of an RPG (i.e., you are playing the role of a character with stats, abilities, etc., that you personally do not have) lends itself to that kind of mechanic whereas an FPS does not (i.e., you are actually using your personal hand-eye coordination and/or other related "twitch" skills). The way the reward systems are set up in each genre leads me to concur that high RNG would punish (again as has been already mentioned by some, above) FPS players, but to a certain degree actually REWARDS player of RPGs.

So yeah, I give you...

Heaven's Maxim: The more RPG, the more RNG!

Heh, just kidding. And come on, you have to admit it sounds better than "MrJoshL's Maxim". Although "Mrrathew's Maxim" does kinda' roll off the tongue! Lol!

Take care.

Luck is a great companion to FPS games. Accuracy is the most prominent luck mechanism that works and no-one objects to it, because it is realistic, to some degree -- you shoot bullets, sometimes bullets miss the target, sometimes you cna land a headshot with a high enough chance to hit the spot you're aiming at.[/quote]
Of course the other edge of the razor in when this happens a little too often, when somehow every opponent manages to get a headshot or take you down in a single bullet. When you unload a whole clip in their neck and they still stand, then they whip around with a pistol and shoot you between the eyes. Then people start to get frustrated because luck is then too noticeable. It's cool to fire a few shots and go "wow I took down this sniper somehow, move forward guys", but it needs to be a relatively rare occurrence so that it can be perceived as "luck" rather than "randomness".

That's the key: luck is not randomness. Luck is the rare occurrence of a seemingly unlikely event ("wow that was lucky"), while randomness is the repeated occurrence of a random event ("wow that was random"). Luck is very important in a game but when it starts becoming randomness it's bad.

People don't mind losing to someone who got lucky every now and then, especially if they get lucky occasionally too. But when it starts becoming too predictable people start to get pissed off because they have no way of changing the odds and are essentially forced to repeatedly lose.

What about a FPS fire from the hip mechanic, where you're "loose retical" is over the enemy, an amount of luck exists here as the shots spread around the targeted area and increasing luck could tighten that retical without visually changing anything. Luck could also simply be an extension of the GUI, here the player earns a "lucky shot" by displaying kill shot locations to shoot to achieve radical ricochet shots against enemies in cover. Lucky buffs to individual shots that couldn't be achieved with that type of weapon could be increased with added luck variable as well. Lucky enemy locked blind fire grenade throws and lucky saved by badge sort of moments could exist where the player’s character pulls out a bible or badge that shows a bullet lodged in it could be fun too (even if myth busters busted this). Variable odds are essential though, even roulette allows you to make "safer" bets by spreading your bets across the board.