I stumbled across this site today: http://www.nikita-ammo.com/

As well as containing some specs for their ammo, wallpapers, and other misc. info, it has a "guess the bullet" quiz. I played it twice and got the whole way to 19! I figured I'd share in case anybody has some time to waste.

(The wallpapers will probably draw more interest anyway considering the popularity of "certain" threads here)