The name of the best 3d puzzle game ever made. Included in Half Life: The Orange Box for Xbox 360, Portal has the gamer solve puzzles by using a 'portal gun' to shoot two portals at the environment: one for an entrance, and the other for an exit, and vice versa. All the while, an computer voice guides the user through each stage, with more ominous comments at each stage.
Guy 1: Dude, lets get on Halo 3.
Guy 2: Hell no. I'm playing through Portal again.