Oh, I forgot to answer the question. Um, what sets me off...

session players who can't keep a beat;
people who drive while talking on cell phones forcing ME to do all the accident avoidance;
president Shrub, except when he is asleep and can do no harm;
bad people taking advantage of good people (see above);
hypocrisy;
disingenuousness;
bad coffee;
"mandatory" gratuities when the REAL problem is that wait-staff are not paid a decent wage in the first place.

And that is just before I get out of bed. Yeah, I am grumpy, too. But I have to be really provoked before I will insult anyone. Once you do, the "discussion" if that is indeed what was transpiring becomes a battle, and all parties lose.