WWE wrestler Muhammad Hassan may be the only wrestler to ever have his character killed off without the wrestler himself dying (at least before 2007 - see below), due to Executive Meddling on the part of the UPN network. After UPN demanded he be removed, his next Pay-Per-View match saw him powerbombed through a metal stage by The Undertaker. Our last sight of him is him laying in a pool of his own blood, surrounded by twisted wreckage.
Vince McMahon himself would later fall victim to this trope, as the 6-11-2007 episode of Monday Night Raw, which the chairman had dubbed "Mr. McMahon Appreciation Night", ended with a stricken, dejected Vince entering a limousine, which promptly exploded. (Perhaps, in a medium known for phony "firings" and "retirements", Vince felt he needed a more dramatic method of writing himself off of television).
Ironically, they were going to resolve the "who killed Vince McMahon" storyline on the RAW after the Vengeance: Night of Champions pay-per-view, if I recall correctly, but then Chris Benoit died in real life. The storyline was quietly dropped, with Vince admitting the whole thing was faked.
Some time after that, they dropped a stage on him to resolve the Million Dollar Mania storyline. Of course, he got better.
Ring of Honor did this with Dan Maff after he royally pissed off Homicide; they wrote him out due to a "car accident." The kicker: Maff was one half of the ROH Tag Team Champions with BJ Whitmer.
Oddly enough, this would happen to Whitmer as well. In the shadow of a long losing streak, he was unceremoniously kicked out of the Hangmen Three when Larry Sweeney bought them out. Even better, the angle was only aired in clip form on ROH's Take No Prisoners PPV.
Happened to the icon of pro wrestling himself, Hulk Hogan, in 2003 during his stint as "Mr. America"; an All American Facemasked persona that did all of Hulk's mannerisms and came out to Hulk's classic theme of "Real American". Payment issues between him and Vince started to create friction backstage and eventually Hogan, who was still playing Mr. America, had his contract ended. The on-screen explanation for this was Mr. America had been "secretly" (as in during off-air segments) pulling his mask off to reveal he was Hogan. Since the whole reason Mr. America existed was so he could deny to be Hogan, Vince "fired" him (which happened after he had already been terminated for real, which makes it this trope).