I always think of that Man Show segment where Carolla and Kimmel are out trying to end Women's Sufferage. Pretty awesome.
On a personal level, I think the most annoying thing I've encountered at protests is how they will draw out all the loons on that side of the political spectrum. Hey buddy, maybe I agree that we need to do something about the evil capitalist pigfuckers, but do you mind if I protest the war first, which is kind of why I showed up today? You saw that with the tea parties, although to be fair the tea parties didn't really have a central message anyhow other than "we're a bunch of crazy fuckers and we don't like that black dude that just cut our taxes".
Oh, don't know if it counts as "protest" or not, but last October/November right before the election someone decorated their truck with a bunch of nutty anti-Obama signs, like "No we can't!", "Obama = Osama", "Don't spread MY wealth around!" and shit like that.