Bioshock

In BioShock, you take on the role of an average guy who's constantly finding himself put in weirder and more troublesome situations. Your plane has crashed over the ocean, you survive, and in your panic and bewilderment, you see a strange buoy. You swim over to it, and it leads you down to a brilliant underwater city that's suffered a colossal war, and it's on the brink of collapse. What helped cause the war was a genetic chemical that scientists discovered could enhance people to do extraordinary things -- far beyond normal capacity. But along with the great physical enhancements come horrific psychological ones….