I have a few. My main one is when someone messages me from a group and doesn't tell me which group they're messaging me from especially if like me, they have their groups hidden.
People that don't look at profiles and, I air quote this one, "Doms". Not the actual dom types, I mean the people that label themselves as one and tries giving you orders when they've barely even said two words to you.
Just yesterday I had a guy message me and started by telling me to call him Sir. I asked why and he said "Just call me Sir." So I said Sir and then he started demanding RL pictures from me. Needless to say, he made the block list very quickly.