A space empire, you build one or more (but usually just one) super-something-combat-gigantic-vessel things. I look for various names for such device/vessel/supership :)

Is your game set in the real world or a modified version there-of, or if not is there an established mythos?

You might go with the name of a fearsome deity, monster or creature if there are any in the setting: Colossus, Leviathan, Prometheus, Thor's Hammer, etc.

No, no, it's just a generic SF.

Preferably I would use some technical name (Battle Station, Stellar Annihilator, Paradox Cube). Also, I look primarily/especially (but not only) for a name for a whole class of these ships. So the final name could be like "Colossus - Stellar Annihilator class vehicle".

Primarily, I want to get a "death star" feeling when the player sees the name of this ship/vehicle class (BTW: how to call this whole thing, it does not seem proper to call it "super ship"...)

You could also try describing the purpose of the ship.

If it is a flying fortress (mostly about fat shields), then it would probably be something akin to Star Fortress or Bastion Class.

If it is a fat flying canon to destroy planets you can name it Planet Cracker or Moon Crusher.

But that is only if it has a "special" purpose (of course ships of that size tend to outmatch most smaller ships on pretty much every field in a significant way).

That's no moon; that's an End of Life Cube.

Unlive Sphere

Penultimate Spheroid Life Remover.

If it is a flying fortress (mostly about fat shields), then it would probably be something akin to Star Fortress or Bastion Class.

Yes, something like this, gimme more names like these:)

About the mechanic. The player will build traditional ships all the time, standard. But he can build ONE special superstation-ship-battlestar-fortress, it won't be that expensive (relatively), actually it would have better power to cost ratio than traditional ships (otherwise the player would not built it :D). It will be a special project, takes long to build (but does not drain that much resources) and once finished you, the emperor, have your cute powerful unique death star thingie :)

It would not be used to destroy planets (but it could have such capability), I want it rather a special-super unit. You send it to important battles or guard important choke points, it would be slow compared to ships.

It may not quite fit with what you have in mind, but I have always liked the names that Ian Banks used for ships in the Culture series. Even if they don't quite fit, I am sure you can get some inspriation from them

-Josh

If it is a flying fortress (mostly about fat shields), then it would probably be something akin to Star Fortress or Bastion Class.

Yes, something like this, gimme more names like these:}

[...]

As you wish:

Bastille Class, Citadel Command Station, Fortification Superheavy Battleship, Castle Control Plattform

That about runs my synonyms dry, but I can offer you some german translations if you find them to sound bulkier or heavier:

Bollwerk, Festung, Zwingburg (this one is a fortress built to control area)