Well I have my no-particular-order set of three here (as opposed to five, since i'm feeling kinda long-winded) as well. I'll add a couple more as the mood strikes me.
- Rockabilly (WWF, April 1997) Augh... this was just painful. Painful to watch, painful to listen to, and apparently pretty painful for almost everybody involved, with the exception of Billy Gunn, who was acting totally oblivious to the still-birth of his new gimmick. The WWF, at the behest of the Honky Tonk Man, were apparently working overtime all early spring to sign away Disco Inferno (Glen Gilbernetti) from WCW to play the part of Rockabilly, who not only has infinitely more charisma, but way better ring skills than our friend Billy. Despite what they say about remakes of gimmicks, I have a feeling that a Honky Tonk Inferno woulda worked. But it all fell through at the last moment with Disco re-signing with WCW, and so they pulled Billy Gunn from his Metal/Jakked-worthy feud with the criminally misused 2 Cold Scorpio (playing as Flash Funk at the time). HTM didn't want him in the role, but Vince was insistent (probably due to influence by Billy's pal Shawn Michaels), so it was done at April's Revenge of the Taker pay-per-view. And by the tone of HTM's introduction, he seemed really embarrassed that he had to be aligned with the guy, and then just decided to get rid of the script and rush through the intro just to get the segment over with. So Billy comes out, has terrible music, dances terribly, and says in a terrible drawl "I AM THE NEW MAN!". Vince and Jerry Lawler, who were on commentary that night, are appropriately stupefied. His first match was against another bad wrestler with terrible gimmick, "The Real Double J" Jesse Jammes. Originally the Rockabilly character was going to go over in a squash, but HTM wanted to get out of the gimmick ASAP so he leveraged with the bookers for a fluke pin in favor of Jesse Jammes. This was Rockabilly's only feud. It ended on WWF Superstars where the two guys decided that they were going nowhere as it stood and made a pact to team up, thereby creating the New Age Outlaws. Which, on the whole, was the most bearable thing for both guys.
- Doink Turns Face (WWF, September 1993) - I'll add my voice to the masses who have already had this thought: the original Doink the Clown was a great concept: the evil clown, spoiling people's fun, playing pranks that make him look more and more heelish. And Matt Borne was great in the role too, so much so that he wanted to take it further. As in, he wanted to turn the role into a demented sociopath roughly equivalent to the Joker, incorporating more of the mind games, and some of the visciousness from his indie days. He really wanted incorporate the new aspects and ideas on his character into with a feud with the Undertaker (who thought it would be great), but it wasn't the Attitude era yet. So Vince nixed it since it was out of the "plans" he had for the Taker. Not only that, but Vince decided it was time for a face turn for Doink. And Borne hated the idea so much, he left. So what did the WWF do? They pulled a Darrin! They got Steve Lombardi to quickly transition the role into a babyface, complete with throwing confetti into the audiences, having other wrestlers that don't even look like the original Doink dress up as Doink for fun (see Survivor Series '93), oh, and midgets... midget Doink replicas at that! Oh man, it was tremendous... tremendously stupid. The Doink gimmick sunk like a rock, and by the tail end of the Doink run, there was always an audible "Kill the Clown" chant. Thankfully, the WWF did. As a footnote, Matt Borne took the evil version of the gimmick to ECW, where he evolved it into the great Borne Again gimmick, where he would dress his beaten opponents up like Doink to make them feel the same "emotional trauma" he did. He had to quit wrestling after almost a year in the gimmick, as drugs got in the way of him having his life in order.
- Glacier (WCW, 1996) - Dun Dun Dun Dun Dah Dah! Dun Dun Dun Dun Dah Dah Dun Dun Dun Dun Dah Dah! (I hated this the first time when it was called) MOOOOOTAL KOOOOMBAAAT! ...actually the material that was used to make the endless promos for this was going to be used for an early version of the Mortal Kombat TV series for TNT, but the producers wanted to hold off until after the sequel, and so as not to waste the material they gave it to WCW to fashion around former jobber Ray Lloyd for a lousy Sub-Zero clone. And the guy, he had bad moves, and bad hair, and bad martial arts skills. And the most laughable backstory in the world, which stole from Kung Fu, The Last Dragon, Mortal Kombat, Highlander, Mamma's Family, and probably about 15 other things too. I do give it some brownie points, though, in that it did introduce the world to "The Cat" Ernest Miller and Kanyon (via a totally silly feud), who later became two of the most entertaining things about WCW in its dying days. It was a such a joke that in the end, Ray Lloyd decided to literally sell parts of his gimmick to other wrestlers, selling the costume to ex-Kaientai DX member Kaz Hayashi and the entrance pyro/effects to Ernest Miller, who just decided to use his own James Brown rip-off music with the Glacier entrance. I think he did some other terrible gimmick after that, Coach Buzz Stern. At least it was unnoticeable.