Rarest RGH/JTAG Homebrew?

I'm looking to create a list of the rare homebrew apps and emulators with download links. There a few classic xbox emulators that work on the 360 as well. Feel free to post and I will add to the list.

Emulators

Amiga360 = Amiga: Link coming soon
Atari7800x (Xbox) = Atari 7800: Link coming soon
CPx3 = CP System I-III (Capcom Arcade): Link coming soon
DosBox 360 = PC-Dos: Link coming soon
Doom Legacy = Collection of ID Doom based games: Link coming soon
exult360...

Rarest RGH/JTAG Homebrew?