"Kill X monster" Quests
Unless your epic RPG involves a plot about a rat plague or something similar, I do not wish to see any quests that involve genocide-by-the-numbers on any creature. Not because I am a preservationist of virtual wolves, but because those quests are usually boring, tedious and only in the game because they are simple to write and easy to explain. Help us, oh mighty hero! Rats have infested our grain silo! Kill X of them to earn five thousand XP! Yeah.
Like hell.
If I have to kill X amount of creatures, make those encounters memorable. Kill the five elemental dragons. There. Now we’re talking. The exeption to the rule is, if the quest is cool enough that you could base an entire game on it, then you might ask the player to kill x amount of y. If not, then you better go back to the drawing board and come up with a quest design that doesn’t bore the players to death.