The Bluetooth people crack me up- I always think that they're talking to themselves so it makes me smile, even when I ask them something and they look at me like I'm dirt.
One time, I had a girl I work with at the registers that was told to shut up by a customer when he answered his phone while she ringing him up.
Happily, she didn't take it lying down. She asked him to step aside so she could ring up another customer. He was pissed, but we backed her (and I think she got a tiny bit of satisfaction from it).
And then there are the times I have had to literally pantomime entire purchases while the customer is yakking away on it.
But you want bad? Try sitting next to someone who answers their phone throughout an ENTIRE MOVIE!!! He kept getting up to leave, coming back.... I tried to tune him out, but that fucker ruined the movie for me.
I paid $10 for this?!