"Libtard" - not because I have a problem with people saying "#######" or variations of it, and not because I have a problem with people insulting liberals... but just because it's a really stupid ####### word.
To be fair to the other side, I also think "repuglicans", or "rethuglicans", is ridiculous, too.
If you can't insult someone without using a silly sounding made-up word, you're not trying hard enough. (Or, you know, just stop insulting people and attack their stance on the issues instead. That would be nice.)
[edited to add - that's funny, I didn't know the board would # out the word that "libtard" is based off of. Interesting.]