Maine has "Every citizen has a right to keep and bear arms and this right shall never be questioned" written into it's constitution, no registration, no restrictions on private sales (as long as both parties are ME residents, and you don't have reason to believe the buyer is intending to use the gun to commit a crime) open carry, and it's pretty easy to get your CCW. Also, it's still primarily rural, there are no major cities, and hunting is a huge money maker for the state, so the majority of the population is pretty gun friendly.
But I agree that most of the gun owners would only put up a fight when something effects them directly, so I'm not sure how an assault weapon ban would play out. I don't think it would pass, but I've been wrong before.
I chose Vermont anyway. Vermont is a rabidly independent state, and most of the Vermonters I've met have been quite apposed to their government restricting their freedom. In Vermont I would expect to see a fairly large percentage of non gun owners vote against gun restrictions as unwanted government intrusion even if they had no plans to own a gun.
New Hampshire I didn't pick just because eastern NH is slowly turning into a suburb of Boston, and I imagine a fair number of transplants are bringing their anti-gun ideas with them.
si vis pacem para bellum