Three hacks I'd love to see fixed:
Cool Or Cruel
(the original): Some music crashes related to clapping chucks or entering a door while a p-switch is running. This hack got me into kaizo.
Super Puzzle World 3
(original download is link from this thread
is down): Broken music. (I couldn't get past the first level due to crashes, so maybe more stuff is broken.)
Super Nerv World
: Broken Music (first crash I encountered was in level 120 "it's a cave, too"). If I recall correctly, taking the warp star in world 3 also crashes the game.