How about an Armalite AR180? This is a neat gun designed by Eugene Stoner back in the good old days of Armalite. It's piston driven, has a folding stock, ambidextrous safety lever, has a unique quick release scope mount design, it's light weight, reliable, and very collectible. Only around 12000 of these produced. Chambered for the 5.56x45 NATO (.223) round.
I might be interested in partial trades, too, like a Russian 1pn34....
http://i89.photobucket.com/albums/k239/jjjxlr8/Firearms/AR180/IMG_2303.jpg