For me, at least recently, it's people who are contrived... People who try to act a certain way to try and fit in, and it's so blatantly fake and forced and ughhh makes me cringe!
The type of people who are more concerned about your reaction to what they say, than what they are actually saying. Like, when planning their response to you, instead of speaking their honest mind, they spew whatever they think will get the right reaction. Like, if I am talking with someone like this, and tell them "OMG I have the funniest joke ever!" No matter what I say next, they will laugh and laugh like it truly IS the funniest joke ever. I could tell them a shitty knock-knock and they would split their sides, because that's how they think I want them to react. And if I open with "OMG I have the lamest joke ever," then whatever I say next (even if it's pants-pissing hilarious), they will react with "oh my goddd you're right, that's awful". Mindless people-pleasers who agree and agree and kiss ass like a sad puppy... Don't they realize that if they had their own opinions (maybe accompanied by a backbone) they would be so much more likable than being a spineless yes-man?
People who always need reassurance from everyone else... they can't have an opinion unless they know the group shares it. "Wow that movie looks good... right guys? Right? Right? It looks good, right!??!" aaaaaaaaaaggghhhh