BioShock

Irrational's 2007 shooter opens with a plane crash over the Atlantic and a bathysphere ride down into Rapture, an art-deco city built on the seabed by a man who wanted somewhere the state could not follow him. It went wrong. The city is flooded, its population reduced to spliced-up addicts fighting over a gene-editing substance called ADAM, and the story reaches you almost entirely through audio diaries left by people who are already dead. Mechanically it is a shooter crossed with an improvisation puzzle: one hand holds a gun, the other holds plasmids that electrify water, set enemies alight or turn security turrets against their owners, and most encounters have three or four viable answers. The Big Daddies patrolling with their Little Sisters are optional boss fights you choose to pick, which is the whole design in miniature. Its mid-game reveal about the nature of your own agency is still one of the most discussed twists in the medium, and the reason people argue about this game rather than simply recommending it.