Man, where to even begin? I can think of a good dozen or so from present-day right off the top of my head. There's tons of former ECW big-names I could rant on and on about (most notably Raven and Tazz), but I want to find the ones that are completely and totally the most deplorable mis-handling of talent. And since I didn't start watching wrestling until the late 90's, I can't really talk that much abut the classics, so these will be over the past five or six years. So, in no particular order....
Ultimo Dragon- quite arguably the best Japanese wrestler ever. The guy can work puro, lucha, whatever you want. And what did they do with him? Nothing. The man could've had MotY caliber matches with Rey Mysterio or Eddie Guerrero or Tajiri (just watch matches from his WCW tenure to see what I mean), and yet the only thing anyone will remember him for now is slipping during his entrance at Wrestlemania. Tremendous: the guy whose name should be up there with the Lygers and Mysterios of the world will now be placed forever alongside the Shockmaster and Mean Gene dropping the F bomb at Survivor Series.
(Oh, and while I'm talking about awesome cruisers who've been utterly destroyed for no reason, I might as well give mentions to Billy Kidman, TAKA Michinoku, Sho Funaki, Matt Hardy, Jerry Lynn, Essa Rios, and Shannon Moore. God knows nobody wanted to see them; we need more Bradshaw, dammit!)
Chris Jericho- I am not exaggerating when I say this man should be the top name on Raw right now. He's got absolutely everything you could want in a wrestler: the technical skills of a Hart, the high-flying antics of a Guerrero, and he can work the mic like nobody's business. During the Rock/Jericho feud in the midst of the InVasion, he was regularly getting cheered as much or more so than Rocky (who was at the height of his popularity at the time) But no, Hunter didn't like him. That's why he's perpetually stuck below even the Intercontinental Title level, while Randy Orton is being groomed for the main events.
Glenn Jacobs- I'm not big on hosses, but Jacobs is one of the few who is a consistently decent worker, has good psychology when it comes to when and where to break out the standard hoss power moves, and seems like a true professional when it comes to his job. So why is he a walking poster for Wrestlecrap? Seriously, look at his long line of woeful gimmicks. First, he was dressed up like an evil Christmas Tree to fight Jerry Lawler in Memphis. Next, he actually had to wrestle as an evil dentist, a concept so ridiculous and insane that it's not even funny to mention anymore. After that, he was forced to pose as Kevin Nash in an attempted ratings grab that blew up in WWF's face (funny, since Jacobs is superior to Nash in most aspects). And finally, he was given a Jason Voorhees-ripoff character for what should've been a short-lived feud with Taker. Instead, the gimmick's been around for about seven years now, with more twists and turns to the character than a roller coaster, only roller coasters are usually fun. So while he's been in a quasi-main-event status for pretty much his whole run as Kane, he's still put up with absolutely ridiculous angles.
Lenny Lane and Lodi- Unlike Billy Gunn or Chuck Palumbo, these guys never really did recover from their gay gimmick. Neither of these guys really had any direction before they were teamed up, but afterwards, the only place for them to go was down. It's a shame, too, because they really weren't half bad. Most guys who are buried or given stupid gimmicks can bounce back in the indies or what have you, but these guys' careers are now completely screwed.
The Renegade- I know I said I'd only do the past five or six years, but this really deserves mention. I wish I knew the guy's real name, since it feels wrong to refer to him by the name of one of the worst gimmicks ever. He was a decent worker from what I've heard, but instead of letting him make it or break it on his own, WCW decided to break him themselves by making him a shameless blatant ripoff of the Ultimate Warrior. The fans shit on it, and he was out the door before you even knew it. He never really recovered from that, and later killed himself. I don't particularly know how good or bad of a worker he was, but I think booking that's bad enough to ruin a man's career and drive him to suicide is pretty awful.
Honorable mention goes to roughly the entire midcard of the WWE roster, and most anyone who ever worked for WCW- especially the guys who are too big to be cruisers but not really big enough to be heavyweights. Don't even get me going here with all the names, but suffice to say there's enough of them to start a whole new promotion.