In Dragon Ball Abridged, Raditz is pretty much this to Vegeta and Nappa. So much so, that they use "a Raditz" as their measuring unit. They can even grow monsters that are exactly the same strength, rendering him completely useless. Needless to say, he's not very happy about it at all.
It Gets Worse. As of season two, in a commercial for "Spacey's," Raditz is now an equivalent of McDonalds's "Dollar Menu."
On the good guy side, there's Krillin, whose treatment as a butt monkey is tallied on "The Krillin Owned Count."
There's also Yamcha, who manages to disappoint people that have never met him and is ignored by those who have.
In the Disgaea fic Disgaea Jewel of the gods Epic is this. But it's not anything special seeing as his whole species, the prinny, are as well.
In the ED-Ucation fanfics, Nazz is treated like a Butt Monkey by Teacher.
This trope is pretty much the entire jokeline of this Toad Strikes Back parody. Lamshaded with 'why are you so mean to me?' 'because... You're TOAD!'
Done for comedy in A Very Potter Musical. Ron and Dumbledore repeatedly harp on Hermione for being a know-it-all, buzz kill, and "ugly." She's the only student in the cast who ever loses points for her house (except Harry, once), often for things that other characters are doing, flagrantly, at the same time as her. Harry is the only one relatively nice to her... because he needs her to do his homework, research for the first task, and everything else he's too lazy to do. This lightens up in the second act, though there's still a few jokes made at her expense.
Carlos in Company 0051, a HaloFan Web Comic. From being chewed out by the Sarge to being the first one to drop out in the boys' Drinking Game, it's clear that his only place is as the local wimp.
Inglorious Bosh'tets, a Mass Effect fanfic, has Tali, the Only Sane Woman of her crew of idiots and Jerkasses, getting this a lot, and whenever something crazy happens, at least one of the crew (often Prazza, who's usually the cause of the crazy) will pin the blame on her.
Spike, from Friendship Is Witchcraft, is very much a butt-monkey. So much so, in fact, that every character has him listed as a dislike in Dragone Baby Gone, and in Read it and Sleep, Spike falls off the roof and breaks both his legs. After disregarding him, Applejack inadvertently drops a log on him, with other instances of disregard or hatred for him throughout the show.
In The Emiya Clan, Lancer is summoned up to help take care of the kids because Gil is getting overburdened with nanny duties. He proceeds to last about fifteen minutes before he gets chucked into a wall by Kumako and riddled with bullets by Keiko.
This gets taken Up to Eleven during the Christmas Special where he gets summoned by Zelretch and Alter!Illya as an expendable source of entertainment. Over the course of the day, he gets crushed, impaled, sliced up, burned, frozen, electrified, smashed in the groin, terrified to death, used as a projectile weapon, and several other things. Oh, and when he dies, he gets resummoned immediately, again...and again...and again...and again...
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