There was a Chris Rock stand-up (at least I think it was him) bit that had me laughing, but it wasn't a terrible idea at the same time. He suggested that instead banning guns, we should just make bullets REALLY expensive, like 50grand. "I would shoot you for saying that, but I already have 2 bullets on lay-away for a guy that talked shit to me last week. You best watch your back if I win the lottery though..."
To combat black-market bullet sales, we can just make the penalty death by a firing squad, a bit of humour/irony