Platform(s): Windows, Xbox 360, PS3, Mac OS X, Linux
Year Released: 2007

Though the sequel is arguably better, the first Portal gets the nod here for introducing a puzzle system that, now seemingly intuitive for the physics of a video game universe, was lauded for its original and refreshing edge upon its release. Using your portal gun, your character was able to hop from wormhole to wormhole to navigate various puzzle rooms that didn't have any set solution, a twist praised by many reviewers of the game. The space for creativity was refreshing, and the level of difficulty left you scratching your head without feeling like you wanted to pull out your hair.