Despite begin terribly terribly fond of meat & well aware of overpopulation's effect on the environment, I still hate it when I have to do quests to kill x number of wild animals or bugs, wishing I'd been tasked with killing some evil humanoid instead.
There was the time when I had to chose between the two grumpy magic users in Neverwinter Nights 2. I always pick the elf because he's cuter, but I spent so much time trying to make friends with both of them. Not that it matters, because ALL of your friends are presumed dead in the expansion.
There was also this one quest back in Oblivion where you become friends with the arena champ & all around nice guy; Agronak gro-Malog, & he sends you on a quest where completing the mission makes him suicidal, & he begs you to defeat him in the arena, not even bothering to fight back. If you give him what he wants, everyone on your team hates you, if you don;t kill him, he just stands there forever saying how much he wishes he was dead. I reject the quest on replays.