Another pet peeve

I always feel bad for the kid who is told by a teacher to look up a word when he/she doesn't know the spelling. Um, how are they supposed to look it up if they can't spell it? It makes no sense to me.

Here is a list of words I always have to "look up". Thank goodness for Google and their "did you mean..." function:

diarrhea (2 rs and an h? Insipid)
fluorescent (the uo gets me every time)
buoy (ditto... it always looks wrong doesn't it?)
rhythm (I always forget the h)
crystal (I always want to put an h in)
anaesthetic (the evil ae)

So what words drive you nuts?

kxx (in the spirit of honesty, I double checked all the above words except for buoy. I can manage not to screw up 4 letters)