Every now and again, I find myself working from behind a firewall and fall back to using Gmail. When I do, I BCC myself on all messages I send (because my POP3 server receives all email and its archived from there and Gmail is just a backup).
I noticed one day that because someone had started addressing me as “‘JavaMan’ <ben@…>” that Gmail decided that my new name was in fact ‘JavaMan’ and whenever I CC’d or BCC’d myself on email, it would use that alias. BCC doesn’t matter, but for CC’ing, it’s actually a pretty embarrassing moniker to start sending around.
I played around with it a bit, and, sure enough, you can override the names associated with any Gmail contacts by simply sending someone an email with the email address given a new name (like ‘ILovePresidentBush’ <yourfriend@gmail.com>).
Of course, I don’t imagine folks are addressing themselves via CC or BCC that often from Gmail, but if your new name for your friend sneaks by just one time… 
Update: Matt Raible commented saying, essentially, “Any email client lets you change the name associated with an email address — just change the value in quotes.” Let me be clearer: Gmail lets you change the name associated with an email address in someone else’s address book permanently (until that someone else changes it to some other value, or someone else changes it). In my case, I didn’t change my own name in my address book to “JavaMan”, but because someone else sent me an email calling me JavaMan, now its changed in my address book.
