Guys who make distracting slurping noises when they go down (makes me laugh, but not horny)
Guys who think they are rubbing your clitoris but they are basically giving you an indian burn somewhere else.
Guys whose sex talk makes me laugh. I once had a guy say "Oh yeah, ride me like a horse."
That was the end of that.
Guys who grab your head and try to play rough while you are going down on them.
Guys who want to go on for a decade when it stopped doing anything for me 20 minutes ago.
Guys who want to switch positions every 3 seconds.
I could go on and on......