People have mentioned Mono, but not Echoes.
Echoes was my favourite Binary Zoo creation. I also bought Echoes+ from XBLA, but obviously that's not a DBP creation, but an XNA port.
It's really addictive, I think my highest score on Echoes+ is about 7 million, whilst on the regular PC version I think 2 million was my highest. It gets really challenging the further you get in, but it's really awesome...and as I said, addictive.
I quite liked Mike Inel's creations, they were really well done, but he never really finished any of them and he kind of stopped posting after he put a hentai easter egg in a game he submitted to an official competition without telling anybody. It did cause a bit of a stir, but meh, people do stupid things and people soon forget that it ever happened.
Dream was awesome too.
Dumbow and Cool was another, it had a review in a PC Magazine, but sadly Drew didn't make much money out of it.