Are you thinking of spending a ton of cash on it?

If you want something that's ridiculously expensive, and no one else has, get an M-2 Johnson Carbine, it's a WWII American para-trooper rifle that has a barrel that screws on, it looks really cool, Cabela's has one on their online gun library last I looked. http://www.cabelas.com/cabelas/en/content/community/gun_inventory/inventory/owatonna/miscellaneous/509646_johnson_owa.jsp

Another:

http://www.cabelas.com/cabelas/en/content/community/gun_inventory/inventory/ft_worth/military_arms/476797_john_fw.jsp?hierarchyId=20005