Halo: Combat Evolved Anniversary Edition
343 Industries released the Anniversary Edition of the original Halo to celebrate the game's tenth anniversary, and it's no mere HD port. Halo's graphics were completely rehauled, and every element of the game was given a graphical makeover that made it almost unrecognizable.
It must have been a gargantuan effort, judging by how prone the game is to freezing up on you and erasing all your progress. Still, if you can get past the technical glitches, it's a wonderful way to experience this classic game.