When I am encountered with an anti-gun fact spouter I turn the tables and go emotional. I ask, in all seriousness how they would feel if they were out with their loved ones and some nutjob criminal opened fire on a crowd and the guy next to them or thier wife or husband or child was shot. How would they feel knowing that they have no way of protecting themselves from this person because they chose to go about unarmed. That because they backed anti-gun laws none of the law-abiding citizens in the crowd were armed and so this criminal, who may or may not have acquired his weapon legally, can fire away without fear from his targets. I ask them how guilty they would feel about knowing that had they supported gun ownership the entire incident might have been averted as generically, criminals do not pick fights with armed citizens, instead specifically targeting those that they KNOW are likely to be unarmed.
Obviously they will initially spout off that if no one had guns blah blah blah, but then I point out to them that in the UK guns have been outlawed and yet look at how many innocents have died in shootings, bombings, etc.? In the cities in this country where guns are heavily regulated there is more gun and violent crimes than in areas where citizens are more likely than not to own and possibly even be carrying firearms.

They talk about "assault weapons" and magazine capacity and why would someone need so much ammo etc. and how it just has to be controlled and so I point out that no matter what, if someone wants to have something or do something, they are gpoing to do it. Drugs are illegal and yet nothing stops them.

Now the intelligent anit-gunner will make some arguments about gun ownership, dangers to children in the home, etc. etc. and how we must "protect" each other from such inherent evil. The most useful thing there is to ask if they have alcohol in the home? Do they support legalized drug use? These are things that definitely present a danger to children in the home and no matter how responsible you are as an adult, are very easily abused by others. Since many anti-gunners are supporters of legalized drug use and "personal freedoms" I find it very satisfying to use this argument against them, as gun ownership, no matter whether it is a .22 pistol, an airgun or a full-on "assault rifle" is a personal freedom.

I also enjoy watching anti-gunners squirm a bit when asked to define or identify an "assault rifle", since many of them have no idea and just pick the black gun with attachments.

I do all this with a serious but congenial tone. I have always found that if you are on the offensive most of the anti-gunners will just get all pissy and whine and shut down and just end up more convinced they are right. Add a little brevity, maybe a laugh or two while still being serious and many will sway a tiny bit. I also offer to take them out shooting so they can answer the question of "why" for themselves.