pimp my gun.com
here's a cool site i found called pimp my gun. its basically like a custom gun utility.
http://pimpmygun.doctornoob.com/ is the link theirs 2 versions the regular one has most guns but is missing some of my favorite guns which are on the old version. the old version also builds shotguns, and pistols.
here are some of my "creations". please, feel free to post your own!