You know what drives me nuts?

Well, to be fair, that list is quite long. However, what is immediately annoying to me are people who send their e-mail in HTML format when they're just writing text. Unless you're someone who constructs elaborate web-page-like e-mails with lots of graphics, fancy formatting and the like, you've no right IMO to be writing HTML mail. It makes it more difficult for those of us who use webmail (which is, like, everyone) or have a shell account (how I miss that!) to see the original text when trying to reply or forward; in the case of webmail, since HTML-formatted content can't be displayed easily in the text input element without manipulation (stripping tags, etc.), most webmail services just punt displaying the original message in replies and forwards and add the original e-mail as an attachment instead. Which makes my life that much harder.

Arrrgggh. I don't care what font you use. I'm not going to glean some obscure meaning from knowing you used Garamond instead of Arial. Why can't people just use plain text?