Da Vinci's iconic The Last Supper, turned into a Team Fortress 2 parody, with—who else—Gabe Newell sitting in the center. If the creator, Nefnoj, used the golden ratio to define the proportions, it is indeed an authentic replica of the original.

Otherwise harmless little things, like the bunny mask from Team Fortress 2, can have a huge impact. For example, it can get someone in the Steam Community to pay homage to Hotline Miami with the game's characters (complete with 80s sunglasses) in a really stunning way.