Those that deny other's experiences and think they have all the solutions. This applies to the "bootstrappers" that refuse to see the systematic causes of poverty to those that deny racism, homophobia, and sexism because they haven't personally experienced it. I find these people more distasteful and damaging to society than actual bigots.
Gum chewers. I can't be in the room with someone popping their gum, plus I've scraped way too much gum off my shoes to see it as a harmless habit ;)
Litterers. Hate 'em.
People that use a speaker instead of earbuds when hiking in the woods. No one wants to hear your crap music, and trust me, you aren't blasting it to "scare off bears," but to be an arse.
Climate change deniers, science deniers, nationalists that parade fascism as patriotism and the people that fall for it hook, line, and sinker.