There are two things that annoy the piss out of me.
The first is when person A is talking TO ME and person B decides to answer for me, even though I'm right fucking there and not incapacitated in the least bit.
The second is when I'm talking to person A for a bit and out of nowhere, person B decides to jump in the conversation and answer for person A. But considering person B seems to have issues letting people speak for themselves, this really comes as no surprise.
I really, really, REALLY wish I had the Brick of Silence.