Fun words:
- smorgasbord
- tintinnabulation
- myriad (much misused)
Painful words:
- tumour
- hernia (topical for me, that one)
And my current pet hate - the ever-increasing use of (for example) 'could of' in place of 'could've' which we all know is a colloquial contraction of 'could have'. It's appearing more and more in writing now, even in print.
OK, I'm a pedant.