Bioshock is a first person shooter/horror game for the xbox 360, pc and playstation 3 by 2K Games.

The game is set during the 1960's where the main character is a plane crash survivor who must explore an underwater city named Rapture.
Rapture is home to a lot of splicers (bad guys) that wish to kill you, and you must fight your way through using weapons and plasmids.
Plasmids are ways of altering your DNA so you can throw fire, or fire electricity out of your hands - this uses up EVE in a similar way to being damaged uses health - and is a major unique point of Bioshock.

Bioshock is an absolutely epic single player game, and I defy anybody to play it in a darkerned room and not be scared by at least some of it - the use of old 60's music gives it a very eerie feel.
The game does not feature any multiplayer modes, so once you've completed the career, all thats left to do is do it again - and it's never as fun second time round.

Anybody with a console or PC powerful enough to run Bioshock should definately play it, you're guaranteed to enjoy it.