The one that hasn't been discovered yet.

The one you don't have.

the ones i have, haha.

dlingy, AeAe is not a species. I think the term you may be looking for is cultivar. There are several other variegated bananas that are much harder to obtain than AeAe. There is an all red banana that could be its own species.
You got many of these out there that are white/green, all yellow, yellow/green, white/yellow/green, white/green/red. Most are one of kinds that have not been reproduce yet nor very stable nor a cultivar. Check out bananas dot org for pictures of some of these.
There's also many of the true Musa species that are hard to find and yet to be discovered.

I believe the rarest might be the AeAe seeds continously offered on eBay.

Here are some rare ones:

http://www.natureproducts.net/Forest_Products/Bananas/Own_varieties/Musa_vinotinto.html