People are still doing insane stuff with the Doom engine, and nowhere is this better demonstrated than with this Donkey Kong mod. The GZDoom mod turns Doom into a whimsical side scrolling platformer, which is obviously quite a change from its origins as a brutal first-person shooter. To give it a go you'll need GZDoom, a download of the mod as well as one of original Doom engine .WADs.
Unless you're intimate with the Doom engine and its modding community, the video below will probably be a bit confusing: how (and I suppose more importantly, why) does one turn a first-person shooter into a sidescrolling platformer? Um, I have no idea, but there's an eerie pleasure in watching a version of Donkey Kong played out with the occasional appearance of old Doom assets. The instructions for installing the mod are over here in the video description.
In other Doom mod news, this is quite impressive .