I'd go with Welcome to Eltingville, if they didn't only make a pilot episode for that.
Full-fledged series that's been cancelled, let's see...Lewis Black wants nothing to do with Root of All Evil anymore, and too many of you guys are gonna say Firefly to make that a worthwhile decision. Very few poker shows were worth getting upset over losing with the whole UIGEA crackdown, so that's also off the table.
...I'ma go out on the farthest limb I can find here and ask for televised coverage of Slamball again. I am a sucker for a good gimmick, and hell if cross-checking a basketball player mid-air isn't a good gimmick.
Diiiiiiiiistant second is the extremely short lived VH1 dating show Megan Wants a Millionaire, pulled after two episodes. I'm curious to see just what sort of debasing activities had to occur on the show for one of the contestants to perform a murder-suicide shortly after it was brought on the air.