Cant wait until the latest game on the MAME WIP page gets added -
http://www.mame.net/wip
Tatooo Assasins, Data East's unreleased MK rip-off that is almost legendry for being a game that was too shit for human consumption. Pretty damn impressive that they managed to get hold of a board for a complete dump, especially considering there are only meant to be 4 in existance.
Some other intresting odds and ends there as well, more Konomi stuff and some assorted Namco things.