I was going to reply a few days ago but I was busy.
I think all items but guns should be droppable. Then, on actual holidays you should be able to "gift" gun vouchers worth x amount if gralats. It's kind of like buying iTunes cards, where you put money on it and redeem in another place. You would only be able to buy one per holiday for a set amount and you can only use them in gun shops.
Or, as Runescape once did, make a voucher system for items. Then you just make a simple "give" command for those. People could trade in their unwanted guns for a voucher (and a fee to put it on a voucher) and give them to friends on holidays.