I chose mine because it was a good design and it was for low points. I hardly ever see anyone who has the same as mine. I think it also kind of shows I'm not some nerd who stays up on AG all night spamming game comments and rating games that I haven't played for points.
I used to switch around every few weeks or so, but this one suits me much better than any of the others, and people seem to recognize me better when I'm wearing it.
Because I like the color blue, and it's the only one I feel like using now. I'd rather use a custom armatar, though. I have one I use on many websites I frequent.
I chose mine because the guy is focused and concentrating real hard which is how I am most if the time. Also its the best out of the first three armatars you get after reaching 100 AG points.
Mainly because I can't have the one armatar I actually like, so I just keep out of the armatar-control-panel until I can actually upload one. Besides, I have never actually changed the armatar myself (always doen by the staff because of new regulations and stuff), and I have no intentions of changing this fact for now. Though, I wouldn't have minded it had defaulted to the black/grey armatar instead of this one. Oh well.