English grammar

It drives me nuts when people make common spelling and grammar mistakes in emails and code comments.

My pet peeves:
- affect vs effect
- calendar vs calender
- their vs they're (vs there)
- separate, not seperate
- peak usage, not peek usage

This one is a bit pickier: Yesterday a co-worker blogged internally about "if I were them" vs "if I were they". I was tempted to comment and say that they were both wrong, due to numerical agreement issues, but someone beat me to it. For the record, "if I were they" is more correct than "if I were them", since the verb "to be" links two nouns of the same case (in this case, nominative). It's the same reason you say "this is she" when answering the phone. But, "if I were s/he" is most correct; since "I" is singular, the other pronoun must also be singular.

I do realize that I'm a complete freak.