As an advertising agency escapee, I'd like to put forth my opinions on the following categories:

Most Hated:
1.) Coors Light football ads (you try explaining to 4 boys that most girls don't dress like THAT or look at you like THAT or wiggle their hips like THAT when they're standing in one place...)
2.) Miller Lite's "Catfight" ad for similar reasons.
3.) Dannon "La Creme" yogurt commercials. Ugh.

Most annoying for no particular reason:
Any Mentos commercial ever made.