Having just got back from an errand on my bike. People who wander all over the bike path without looking around for other traffic and then look affronted when you cough and say "Excuse me." when you want to get by. Yes they have as much a right to be there as I do. That right means sharing it not hogging it! HHRUMPH!

Having to spend discussion time in a meeting or class catching people up on material they should already be familiar with. Used to drive me up the wall!