Thought of two more over a Friday lunchtime pint.
One of my favourites, though an indirect one was coined by someone famous, probably Groucho Marx: Someone said "X is his own worst enemy you know," to which he replied "Not while I'm alive he isn't" - pure class.

The other one was pure me.

I'd just started the job from hell. Packing chocolates as a temp for a famous York based chocy producer...on the night shift. Our supervisor was an evil 24 year old townie slapper who really enjoyed shouting, and would have cracked a mirror with just one glance. It's actually pretty hard to pack two chocolates in the right place in each tray as they whizz past you bumper-to-bumper at the rate of about 2 per second, so she was shouting at us to speed up. I was a bit pissed off with her attitude and said
"I'm going as fast as I can", she came back with something like,
"Any more of your back-chat and I'll make sure you don't come back tomorrow night", to which I replied quick as a flash,
"Ooh, that would make me cry" in my most sarky manner. Anyway, it shut her up for a bit and the whole production line (about 20 of us) smirked and giggled at her for the rest of the shift.
(Che Grimsdale Best before:, Fri 30 Apr 2004, 14:29, Reply)