I'm a bit of an English nut, so for me spelling words isn't very hard. People always come to me to spell things for them. Soo, I usually don't mind.

And I don't think there's a word that I'm really uncertain to spell. Things like "occasion," "necessary," etc. Used to always trip me up when I was younger. And I would like.. Completely avoid using those words if I couldn't remember how to spell it.