Players who refuse to tell other players their character's name let alone class or race or other get to know you/what can you do so we can play well together trivia.

Players who keep party treasure to themselves.

Players who run off to have their own solo encounters. This has nothing to do with scouting and reporting back.

Players who constantly pass notes to the DM even if they don't say or mean anything to be mysterious.

Players who learn important information and refuse to share it with the party.

Players who pompously tsk tsk when other PCs are in a pickle.

Players who refuse to help other PCs when they are in a pickle.

Players who help other PCs when they are in a pickle but pompously exclaim what idiots they are they need to be saved again.