What I'm looking for, are your stories of AI that, once you knew how they worked, have ruined a game or entire genre for you.  And counter to that, what are AI's that when you know how they work, make you like the game even more?  Especially 

For me it was racing games that were ruined. They used to be my favorite, until I understood enough about the AI to make them fun.  I.e. They present an epic struggle keeping me engaged, until really close to the end, where I finally win. But then going through enough AI development on other games, to provide the right amount of challenge but to still allow the player to win.

Now that I know that the AI chose to keep cars with me in stages, then at the last minute, I get to watch the race car I've been neck and neck with, they just suddenly start to go slower.  I used to love that, but now I feel like I'm a little kid that the adult is letting win.  

On the counter side, creating is biome AI's.  I've absolutely loved the complexity of some of them, and feel inspired when I see more interesting environments.  Minecraft's Biome and World-Building systems are an incredible AI for effectively being pixel art.  

So let me know your stories, what AI's do you hate, which one's inspire you? Any recommendations to improve the ones you hate, or should they just be thrown out?

 - Thanks.