I forced myself to learn the NATO Phonetic Alphabet a long time ago (did not serve in the military, but thank you to all who did), and it freaks people out when I spell things! Some people are all, "huh, November?" I'm an IT consultant, so I'm constantly rattling off serial numbers and other codes over the phone. I literally had a wallet-sized print out of it that I would carry with me and would use pretty much daily.

Also, it was annoying hearing myself say, "F as in Frank", "N as in Nancy"...