http://www.overclock.net/customavatars/avatar86820_41.gif, because 21 and 24 are the greatest duo of all time.
My current avatar because it's Halloween, and Halloween III: Season of the Witch is a horribly underrated film. I also find http://img89.imageshack.us/img89/6183/fdb.png to be creepy for some reason.
Mines of a generic Helghast foot soldier. I set that as my avatar when I was hyped for Killzone 2 and never changed it. It's still relevant as Killzone 3 is now my most anticipated game.
Mine's of my favourite sketch card From the Marvel 70th Anniversary set, the character is Jewel and the artist is Kristin Allen. I'm not into Marvel or comics, I just collect the sketch cards.
My current one is Darth Revan (or it's him before he took on the Darth title) and I chose it because I like the character, and I have a thing for robed/cloaked figures. I've considered changing it though, but I haven't come around to it yet.