My biggest bugbears are conversational:
- Interrupting / talking over someone;
- Guessing the end of sentences and being repeatedly wrong;
- Failing to listen when someone speaks to you (briefly, not at length) and not even noticing if they trail off part way through a sentence once they realise they are being ignored.
Nothing more clearly communicates a total lack of respect or utter self-absorption.
I work with someone who is a monster for all of this. I once had a farcical exchange with him that went something like:
Me: I think we need to get the figures...
Him: out by Monday?
Me: No. We need to get the figures...
Him: Balanced with the email we sent on Weds?
Me: No. The figures...
Him: Need to be reduced?
Me: ... No.
Him: Need to be increased?
Me:....... No.
Him: ... I'll just let you finish, shall I?
Good idea.