Driving (in addition to what's been mentioned previously):
People who lack any ability to maneuver their vehicle. For example, people who have to come to a complete stop to make a right hand turn.
People who don't turn into the nearest lane. People should be able to turn both right and left onto a two lane road (two lanes in the same direction) at the same time. It's especially bad when there are two turn lanes, and one of the people can't stay in their lane.
People who can't park. If you don't know how to drive and your car isn't in the parking space, that's bad. If you're too lazy to move your car once you realize that you're on the line and taking up two spaces, that's even worse.
Cell phones. Yes, those god-forsaken contraptions get their own cagetory:
People who think their cell phone conversation, texting, dinner, etc is more important than paying attention to the road while driving.
People who think their cell phone conversation or texting is more important than getting out of the damn way in the grocery store. I want to go to a store, pick up what I need, and get the heck out of there. If you want to have a conversation, go find somewhere out of the way to have it. Don't stand blocking the aisle not shopping while you talk.
People who think their cell phone conversation or texting is more important than the people they're actually with. When I'm out with someone, I expect to interact with them, not to watch them hold a conversation with someone else. I can think of very little that's more rude than ignoring the person you're with to talk on the phone.
Miscellaneous:
People who think everybody wants to hear the details of their personal life. Forgive me if I don't care that you [casual acquaintance/friend at work] finally got your period.
Lastly, people who piss and moan on an internet forum about trivial stuff that "really grinds their gears." Especially people who make really long posts, sorted into multiple categories, about these inconsequential annoyances.:th_winking: