Using the term "far right" to refer to neoliberals/libertarians
Using the term "far left" to refer to left-liberals
I would expand on this:
The use of the term "liberal" to describe any left-winger.
The use of the term "conservative" to describe any right-winger.
It's particularly irritating when Americans apply it to other nations' politicians and parties. "Liberal Gordon Brown" just doesn't fit at all.
Others peeves of mine include - citing the Founding Fathers/U.S. Constitution (or some other historical figures or documents) in every argument, the fact that Iowa and New Hampshire have waaaaay too much say in who the President of the United States should be, and (in a more general sense) the fact that most people in liberal democracies just don't give enough of a damn.