"Holding the door open for people twenty feet away."
+1 I hate it when people do that xD
Wizzing all over the toilet seat. ( Yeah, they can wipe it off if they notice it, but that still sucks for them )
Oiling the steps
Using the doorknob as a tissue
Taking your time ordering your food - knowing how pissy the people behind you are getting each time you change your mind.
Emptying the gas out of cigarette lighters, wetting matches.