Deus Ex is pretty enjoyable, I'm actually replaying it now on the hardest setting. It's flawed in a lot of ways, but you only notice because how good it actually is. If you can get the game of the year version for $12-15, definitely pick it up. There's a multiplayer too, that's pretty involved, to the extent that I haven't bothered with it, but is probably pretty rewarding if you give it a chance because you can customize your player in a bazillion ways (weapon specialty, cloaks, thief and tech skills, regeneration, the ability to pick up giant boxes and block passageways, take over turrets, see through walls, super jump, etc...!!!)