I want to emphasize that so I don't get weird personal messages or the like from someone feeling called out. The things that annoy me, or annoy you, may not be bad for every tabletop group or campaign story, and may even be fun for some groups or there may be exceptions that make them bearable and so on and so on. :zizek-ok:
With that disclaimer aside, I'll list some of my pet peeves, both when I'm running a campaign and when I'm playing in one.
The exile that doesn't actually experience any stigma or negative social consequences for being exiled, but the player insists that the character is exiled somehow because it sounded cool and badass. This gets extra annoying if the exile thing nearly becomes a plot point but that plot point is thwarted because the person playing the exile starts to complain about it.
"The last" whatever they are. Some wonderful stories are about someone being the last of their kind, but when it's used as a cheap and lazy gimmick to try to make a character seem special in a paradoxically basic and commonly-used way, it annoys me.
The walking talking powergaming template. Yes, I can tell that the player knows the rulebook and supplemental materials well, but when asked who the character is, this is the person that talks about the template's superiority and often can't come up with even basic character motivations besides "win and dominate in a game that is supposed to be about cooperation and interactive storytelling."
Direct lifts from any existing well known IP. They aren't just uncreative; I have yet to see a player play such a character convincingly or even design the character well enough to match the intended material. I might actually be impressed if someone pulled it off for a one-off or casual campaign.
Characters that are just the player in real life, but transplanted into the setting with better stats and cool powers. I think it's nearly impossible (and probably not worth the effort) to try to play a character that has absolutely nothing in common with the player's personality, interests, quirks, or the like, but with that said, a direct player-is-the-character player is almost always going to be trouble. In my experience, setbacks, injuries, and especially death can and often will make such players take it very personally, get vindictive, and sometimes have an Epic G*mer moment that can get profane, even violent. Not fun.
My big one is characters that players try to justify "power gaming" with
Just because you say Ragthor is Half-Angel, Half-Demon doesn't mean you can give them 20 in every stat and immunity to elemental damage
I considered ranting about half/half/half/half specialness-binging fantasy eugenics enthusiasts, but I'm glad you brought it up first.
Yeah, as someone of mixed ancestry myself, it's a really big red flag when people treat fantasy species like dog breeds
It just gets gross almost every time
If the rules of the fantasy setting really did do "hybrid vigor" ideology to that degree, what would stop some eugenics-obsessed villain from weaponizing that ideology and making truly absurd hybrids in some evil laboratory?
I don't allow half angel half demon half vampire nonsense template stacking character concepts anymore, but if I did, I'd be tempted to roll out the above villain concept, and maybe even subtly dunk the powergaming player by making them realize that they were just a stepping stone toward the really powerful super hybrids that came afterward, maybe some amoeba-like Akira-style blob. :troll:
On the lighter side of things, I made an entire civilization of "Half-Elves" that didn't call themselves that because their shared ancestry had cultures and traditions woven together in an inseparable way. Both Humans and Elves were seen as outsiders to their own kind because they did their own thing as one people long enough.
I really liked them, too. I took inspiration from Maori, Incan, and Ainu sources to make something new.