Something like uniques in hell's armory could be a good thing - but it should be randomish: no crappy uniques like FUCKING BUTCHER'S CLEAVER STOP FUCKING SHOWING UP GODDAMN FUCK FUCK FUCK FUUUUUUCK
also
Medal ideas:
You suck!: Die on level 1 (can't get this on Nightmare!)
Kornel is not amused: Beat the game (whole game: every challenge and stuff) on Nightmare! (maybe force the player to get every other medal?)
Embodiment of Rage: find the butcher's cleaver
12.0 on the 10 point scale of badness: Full win a game using only your hands (this includes going to every special level and 100% kills)
RNG's lover: Survive something usually not survivable (switch of level lava flooding, anyone? also, getting this makes the RNG slightly favor the player [no butcher's cleavers, special levels spawn mostly at the best time to face them, monsters miss slightly more, etc etc etc])
Xom is amused: win on Ultraviolence/Nightmare!
Losing is fun!: lose the game
Also, how about a BLADE difficulty, that would be fun... and by fun I mean FUCK YOU KORNEL WHY IS THIS SO HARD YET WHY DOES THIS FEEL SO GOOD