The things that drive me absolutely crazy in almost evry circumstance know to man:

Dragging Complainers: The people who complain about certain things like work and do NOTHING AT ALL about it.
Example:
Bob:AWWWWWW!!! I HATE my job! I hate it! My boss hates me. I hate my boss. My coworkers are weirdos who have absolutely no life at all. I want to be fired! That's right! Fired! That is what I am going to be soon! Fired. You hear that, COMPANY NAME HERE? You are going to fire me!!! And I will be very, very, very happy about it!

Me:... Why are you telling me this? Just asking.

Bob: AWWWWWW!! I HATE you! I hate you!

etc...

People who insist on doing things at the most inappropriate time: people that.... yeah...

Example:

Me: Well, lets get this meeting started. How far are we in the planning process for the new product, guys?

Bob: Ummmmm.... I uh... REALLY have to go to the bathroom. I mean, really. It's getting REAL BAD. I can feel the little insects just-

Me: Uh, ok. Moving on...

Bob: The insects, man! They are crawling all over my-

Me: AHEM. MOVING ON...

Bob: THE INSECTS ARE EATING MY-

Me: Bob, would you like to leave?

Bob: IT'S A RIVER OF BLOOD!!!! AAAAAAUUUUUUUUUUUUGGGGGGGGGGHHHHHHHHH!!!!!!!!!!!!! !!!!!! HELP ME!!!

Me: I quit.

TMIers: The people who give WAAAAAAAAAAAAAAY too much information about things better left unknown.

Example:
I'd better leave the example to your imagination...