Many years ago a friend of mine was showing off a band that he liked, and he decided to get more information about them from their website. This was back when the internet was still spelled with a capital 'I', AOL was the most common email provider, and businesses hosted their websites on Angelfire. We waited for a while for the images to load, and when Netscape finally showed us the website, I was delighted to see that one of the cartoon-styled drawings of the band members looked like me! (Or, at least, he wore glasses, had a combover, and was sporting a big grin.)
I saved the image and put it on a floppy disk for storage, and have to this day used that simplistic drawing as my avatar online. The problem is that it's not my image, neither of me nor owned by me. Thus, after many, many years of use, I finally sat down and created a new avatar, made in my likeness.
I used Inkscape for everything. Thanks, open source!
Update - David has posted a delicious parody of this post on his blog. Check it out!