Like Jay, "I could care less" is one that bugs me. If you could care less that means you care, as you still have room to care less.
I hate the mispronunciation of commonly used words even more.
It's height, not heighth.
It's especially, not expecially.
It's escape, not excape
It's asterisk, not asterix.
It's ask, not aks.
It's jewelry, not jewlery.
It's realtor, not realitor. Actually, it's Realtor, but I can deal with people treating it as a common noun instead of a proper noun.
And for God's sake, it's nuclear, not nukuler, or however the heck you would spell that word. I thought pronouncing it as nukuler died out with the Reagan Administration. 
That's just the tip of the iceberg.
Yeah, I'm kind of picky when it comes to pronunciation.
