9. Speedrunning The Co-Op Mode SOLO - Portal 2
Playing a video game in an unconventional way is one thing, but literally betraying the established rules of said game is something else altogether.
Whether for the sheer challenge of it or because they couldn't find anyone else to play with (d'aww), a small but fiercely committed number of Portal 2 players endeavoure to not only beat the game's co-op mode by themselves, but do it as a damn speedrun.
In many games designed around co-op play, it's simply physically impossible for a single person to execute the multitude of commands intended for two players, but if you're nimble and creative enough, Portal 2's co-op campaign can indeed be beaten without an extra pair of hands.
Aside from a few tricky sections near the end of the game, most of Portal 2's co-op doesn't actually require precise synchronisation between players, but even so, the fact that speedrunners have been able to beat it in less than 40 minutes is nothing short of astonishing.