I had one idiot, who was a friend of a friend, who had a thief/assassin.<quoted text>"Go ahead, annoy the DM.
It's your soul."
Laffin. Once upon a time, yes, even I went there.
That was fine-- thieves are a long tradition after all.
But this idiot insisted he could "assassinate" a monster-- mid-dungeon crawl!
He was one of those rule-book "lawyer" types. I tried to reason with him-- as the DM, my world-- my rules.
He wasn't having any... he insisted, in spite of the description indicating that assassination was something that required at least a modicum of prep-work and planning, and wasn't "just another way to attack in melee".
A few turns later? Imagine that-- the mother-of-all piercers dropped out of the cave-ceiling, onto his assassin character.
Rule 1 of D&D: never argue with the DM, who **literally** controls the gods of the campaign.