Annoying things... I don't know if I'm the only one who notices this, but I sure do get annoyed when I'm biking and a dog chases me. Especially when I'm going down a hill, building up momentum to get up that next hill, and the stupid mutt starts barking and running right at the bottom of the hill. I have to come to a stop, point my finger at the dog and say "NO!" and then start up the hill with no momentum at all.
Stupid dog! You ruined my inertia!