Just be aware that if you use paypal for a prohibited item, and later need to dispute the transaction (gun not as described, broken, lost, ect), paypal will do NOTHING to help you, and will most likely lock both the senders and receivers accounts indefinitely (along with any money you have sitting in either account). Paypal is not a bank, and does not have to play by the same rules as a bank does, they can pretty much do whatever the hell they want with your money (which is why I never leave any money sitting in my account). I would have to imagine using "gift" also gives the sender little recourse in the case of a deal gone bad, so I'd only use that option if the money isn't a lot, or you implicitly trust the recipient.
As far as being difficult to get $ back on a deal gone bad, how I understand it is paypal can get your money back if its still in the paypal account, but if its already been transferred to a bank account or withdrawn from an ATM, there's nothing they can do, except block the acct from future transaction, and possibly garnish what your owed from that. Thankfully I've never had an issue as a buyer or seller when paypal was involved, but am still as careful as can be when it comes to paypal.