I think the most implausible finisher (ok, I know I'm changing the subject somewhat) is the unprettier or kane's tombstone cos he's absolutely AWFUL at delivering it.
Petey williams finisher is bloomin good, I loved CM punk's finisher he did off the top rope when he was in ROH and CZW, kinda like a pedigree from the top rope. My fave finisher is probably brock lesnar's F5, visually quite spectacular.
Also, thank heaven for jeff hardy! that is all.