These are called "jobbers" in the business - wrestlers whose sole purpose is to regularly come out and be on the receiving end of a Squash Match to try and put the other wrestler over as dominant and/or a heel.
Santino Marella. When he's not doing something to hurt/humiliate himself (like trying to mimic Melina's entrance, which involves doing the splits, and hurting his crotch in the worst possible way) or getting dumped when the dummy he's dating abruptly grows a brain, he's getting mauled by everyone up to and including the weakest females on the roster. It was vaguely implied his former girlfriend Beth Phoenix occasionally beat him up just for the hell of it.
The ultimate humiliation in pro wrestling has to be when one of the fan favorites screws you over and the audience thinks it's funny. That's what happened to Santino when Shawn Michaels kicked him in the face backstage when Santino was rehearsing his "acting skills."
Following his face turn, Santino seems to have Took a Level in Badass and became a more competent tag team partner of Vladmir Kozlov. Since his overall quirkiness still remains, he still gets it once in while, but then again, how many comical wrestlers don't?
As of the 3/5/12 episode of Raw, Santino has taken another level in badass after winning the United States Championship from Jack Swagger.
Chavo Guerrero as well. While not as great as his uncle Eddie, Chavo's a pretty solid wrestler, but constantly gets stuck in this position. Hell, he's in a months-long feud where all he does is repeatedly job to Hornswoggle, the wrestling leprechaun.
There's also a long running joke among the RAW guest hosts as to who can humiliate Chavo the most. This has resulted in him getting beat up by the likes of Snoop Dogg and Bob Barker.
And don't forget the original Butt Monkeys during the WWE's "Attitude Era," the Spanish Announce Team, whose table would be broken in just about every episode of Raw.
It's still in effect, even though it usually only appears at Pay-Per-Views these days, if you see it, you know it isn't surviving the night.
Shannon Moore....where do I begin? Was treated this way by Matt Hardy at the height of Mattitude, often getting physical attacks for losing or costing Matt a match. When Matt defected to Raw, the role of Shannon's tormenter went to Paul Heyman, who continously booked Shannon in unwinnable matches (though Moore defeated A-Train) and rigged a poll so he would be Brock Lesnar's opponant for the WWE Title.
JBL later pulled the same trick, rigging a poll in order to beat up Moore, which he did rather easily. Poor Shannon
Tara could have possibly been considered one since she arrived in TNA. First she had to face ridicule from then-Knockouts Champion ODB for being a "(WWE) Diva," even after beating her for the title. Afterwards, her pet spider Poison is stolen by Daffney Unger and only manages to get it back via an event which also leads to her losing her title in very ridiculous manner (See the WallBangers page for more info) and when she does get a chance to get the title back, it's via a tag match in which she gets pinned! That in particular seemed to be the last straw as, like Eric Young above, she had pulled a Who's Laughing Now? style Face-Heel Turn. Her tenure in TNA columnated in losing a career vs. title match against Madison Rayne...
Only to return after spending about two months "disguised" in a biker outfit, win the Knockouts title in her first pay-per-view match back, and then drop the title on the ensuing edtion of Impact by BEING FORCED TO LAY DOWN FOR MADISON. And let's not even start with the majority of her run in WWE as Victoria, where she would job to anything that moves, wear ridiculous Haloween outfits, and even dance like a fool at one point with no explanation.
Jamie Noble. Other than managing to beat up CM Punk and Chuck Palumbo, and being one of the first guys to put up a serious fight against Vladimir Kozlov, the last few years of his WWE career featured him getting pwned by the likes of Hornswoggle and Vickie Guerrero.
Believe it or not, this trope also applies to WWE Chairman Vince McMahon himself! He never wins at WrestleMania (go ahead and check), was the personal punching bag of "Stone Cold" Steve Austin for a good two years, and was subjected to a seemingly never-ending Humiliation Conga (having crap dumped on him, getting peed on, nearly getting blown up, etc.) when DeGeneration X took over Monday Night Raw in the summer of 2006. Granted he brought it on himself a lot of times and on occasions often dished out as much as he took (the DX feud for example was in retaliation to an endless amount of abuse and humiliating stipulations handed to both HBK and HHH after they got a little too impudent around him) but still his indignities often overshadow the majority of examples here.
Vince comes off as almost heroic in these cases when you remember that this punishment he takes is completely by his own choice. Look it up, he never, ever comes out ahead in a feud. Even in the rare cases where he's the face, The Bad Guy Wins. Vince pretty much says that he's a natural villain and shouldn't come out on top.
Ken Anderson. In just one week, he was assaulted by: Sting, Sting again, Matt Hardy, Abyss, Sting again again, Sting a fourth time, Hulk Hogan, Sting yet again, and Rob Van Dam. Seems like people just can't resist beating up the asshole like Sting.
Oh, boy, Jillian Hall. Hell she could even be the new trope namer, crossed with The Woobie. Around 2007 they gave her a Hollywood Tone-Deaf gimmick as a Take That to Brooke Hogan who was trying to have a music career. When she got moved to Raw she became a joke and jobber and existed for four years being mad fun of for her bad singing. The problem was that the fact that it was supposed to be a mockery of Brooke was never really spelled out, thus it seemed like Jillian was just sent out to look like an idiot for no apparent reason and who had no idea how badly she came off to people. In both 2009 and 2010 she had only one pinfall victory that she got herself. She actually managed to capture the Divas' title from Mickie James...only to lose it to Melina about two minutes later. Then there's that one-sided feud with the Jerk Sues the Bella Twins.
Molly Holly circa 2002, during the 'junk in your trunk' angle where her entire existence was an excuse for people to make fun of her derriere - especially since she was Women's Champion at the time! She actually managed to make it worse by allowing it to be revealed on more than one occasion that she wore granny panties.
Zack Ryder seems to have been reduced to this as well in recent times, as he has been getting repeatedly pummeled by Kane, humiliated and used by a scheming Eve Torres, and jobbing to wrestlers who are less popular than him (usually after a crowd-pleasing Broski Boot and a failed attempt to pull off a Rough Ryder).
He finally gets his revenge on the 7/3/2012 edition of Super Smackdown, by eliminating Kane from the battle royal and throwing punch on Eve.
In the lead up to the 1,000th episode of Raw, Heath Slater fulfilled this role, with his overzealous ego causing him to run afoul of WWE legends, who are more than happy to put the One-Man Band in his place.
A variation is Billy Gunn, if only because of how Ken Shamrock brought so much more enthusiasm to the task of beating him up than anyone else did, with no explanation ever offered.
Dragon Gate's Naoki Tanizaki. He came from through the Toryumon training systemnote Ultimo Dragon started a promotion called Toryumon, he later left/was forced out of the promotion but took the Toryumon trademark with him, forcing it to rename itself Dragon Gate and apparently someone's unwilling to let him forget it. He's been put in way more than his share of humiliating angles, e.g. being forced to wear an olympic-style speedo swimsuit and then lose cleanly to Stalker Ichikawa. Most recently, he lost the rights to his name to the former Tomahawk T.T., who's getting more of a push impersonating Naoki than Naoki ever did. And he was forced to change his name to Mr. Kyukyu Toyonaka Dolphin.
Miss Elizabeth, particularly for every storyline starting with Randy Savage vs. Honky Tonk Man feud. In the process, she's been shoved to the canvass several times (and sexually harassed several times by the same man), had her wrist nearly broken by a man three times her size, was pulled into the ring by the roots of her hair by a man six times her size (the same man also broke her ankle at least once), was thrown across the room by an irate Savage ... just less than 15 minutes after Savage was thrown on top of her and knocking her out, was verbally abused by "Sensational Sherri," was repeatedly targeted by Jake Roberts for his satanic games (including being slapped, made to grovel for Savage's safety, slapped again, and nearly had a snake thrown on her to bite her!), and scandalized at least twice (including once by Ric Flair).