A Sega Genesys emulator with sound.
A SNES emulator with sound.
In both cases a native (OCS/ECS/AGA+paula) and RTG+AHI version would be really cool.
There is a an old version of AmiGenerator that works on a 68040, but has no sound.
There are many 68k SNES emulator that dont have sound support and are incomplete in one way or the other.