Oh geez, I just made a whole thread about pet peeves I have about other players, because I'm trying to figure out how to manage it when I start running. Well, here they are, and a few more:
1. Not being intelligent with your spells, then demanding a long rest. Especially if you're a healer, and you're now counting on the bard to do the healing for you.
2. Interrogating NPCs who clearly don't have any more information for you.
3. Doing brazenly stupid things, then being surprised when people don't react positively when they fail.
4. Playing the same character archetype over and over and over again. This one player plays the same flirtatious, "I bang anything that moves" character in every single game we've played in so far.
5. Not being prepared when it's your turn; I understand that things change (your chosen enemy might die, or the spell you had planned won't work after the last player's turn), and I can give grace for that. It's when every single time it's your turn, and you react like a deer in headlights that I start getting annoyed.
6. After playing DnD for a year, still not knowing that when a DM asks you if their attack hits that you should look at your AC score. Yes, this has happened with the same player. Over and over again.
7. Not being willing to be flexible with your character when the rest of the party wants to do something. Ask me about the time when a lawful evil NPC asked us to do something we were already going to do anyway, and offered us help to do it anyway, and the paladin wanted to decline their offer and kill them and all of their considerable lackeys. We only barely managed to convince her not to get us all killed by picking a fight, and were forced to decline her help despite the fact we were doing the thing she asked anyway before she even came into the picture.
8. Doing things that obviously make it difficult for other players to play their character effectively in combat; I don't expect players to know each other's characters backwards and forwards, but after a year of play together, I'd hope that one player would know that the paladin is capable of taking another action after they KO an enemy, and have the intelligent to attack the full-health enemy next to the paladin instead of the almost-dead enemy in front of the paladin.
I know some people said they don't appreciate people doing other things at the table, but I'm a notorious doodler/artist during game sessions. I know I made a DM mad back in high school for doing this because he felt that I wasn't paying attention, but it actually made me more focused; I'm typically very anxious, and drawing allows me to direct that nervous energy into something so that I can pay attention to what's going on in front of me. Hoping this gives some DMs who find this particularly peeving some insight into why some players do that. (I'm typically drawing my DnD character anyway.)