Dave Taylor...
Yeah, that's right. Taylor was on the roster and not being used for about a year before his release. He was in one of the greatest WWE tag team feuds/matches in recent years (MNM vs. Hardyz vs. Regal & Taylor vs. London & Kendrick) and then when Regal was drafted to Raw, Taylor went on to make 2 more TV wrestling appearences. He did manage Drew McIntyre in October, but didn't wrestle. He may be 51, but for someone who is ranked 429 out of 500 on PWI's list of best singles wrestlers, he is ranked #1 on my list of best wrestlers never to win a title (single or tag) in a major organization (WWE, WCW, ECW, TNA).
(source for a lot of the info: wikipedia)