Here's another to stir the pot. Suppose you are sitting in your apartment one evening, when you hear a disturbance.
[peep]
Peeping out your window, you witness several youths from a nearby bad neighborhood menacing a resident of your complex, one you know would not go looking for trouble. It appears to be an assault in progress rather than simply kids being kids. Do you:

a) Turn up the volume on the TV? [sleep]  
b) Call the police and watch from inside? [rolleyes]
c) Call the police and then go outside to intervene? [pissed]
d) Go outside and intervene, and call the police later if at all? [whacko]

If so, what would bring with you? Why? [thinking]

I'm thinking Option C, and I might bring my AR-15, w/ Eotech on and a 30rd clip. A shotgun might be impractical if you get into it and friendlies are mixed in with hostiles due to pellet spread. The limited shots available to a shotgun might not be enough to deal with more than one or two assailants with pistols. Also, the mere appearance of a neighbor armed with a scary looking assualt rifle would very likely overawe the hostiles, making them flee rather than fight.

c. i might tuck my 1911 in my belt, in back so as to be non-confrontational. no point in letting them know i'm armed until i need to.

I would go to assist but with my weapon concealed. I would only show it if necessary.

Good point there, but I'm wondering if it might be better in a case like this to be scary from get-go in hopes of making them run rather than fight.

I would pick option D. I would immediately go outside and intervene. In the amount of time it takes to call 911 and talk to the operator it could all be finished and irreparable damage could have already occurred.

I'd take whatever handgun I had close and would either stick it in my pants or conceal it some other way. My presence my be enough to stop the assault, but should I need a little help I would have it. I would want it concealed because there is no use showing your whole hand all at once since it would be a last option choice.

If it looks like they want to fight me that is when I pull my weapon. If they still want to fight, that is when people start springing "leaks".

As above, except dial 911, leave phone off hook, grab handgun (concealed), go outside.

I would pick C. Probably pack a concealed pistol outside, don't want to escalate things and don't want any other possible witnesses claiming I "assaulted" these kids by brandishing a weapon.

Might also call out the window that the cops are on the way

I'd take a couple of concealed handguns, and call the cops and walk out with the cell phone in hand. The presence of another person MIGHT be sufficient for them to run. If that doesn't work out, the hand gun might be handier in the melee that is likely to follow. Also, YOU will have avoided escalating the violence by your response.

If you walk out with the AR15, if things up close appear different than they did through the window, you have already committed a crime in most states.

And when the law gets into the act, it will be: "Honest, we was just funning with the guy and this nut walked out with an assault rifle! We was scared to death, and we want 60 gazillion dollars cause we cain't work at McDonalds no more."

"Thats right yer honor, we was assaulted while we wasn't doing nothing in the parking lot."

Also a very good point. Pistol makes a lot more sense. My initial reaction of grabbing the AR is plainly a leftover from too many Charles Bronson movies...

This is tough and easier to state when thinking about it. I believe I would skip the 911 call as someone else would most likely be making the call. I would grab the 1911 and a spare clip in pocket, rack the slide as I aproach outside tucking into front waistband (This would be skipped if I noticed a weapon wielded, and direct shot would be fired to that armed attacker if they were attacking). The distanct racking might be all it takes to disperse them, if not I am ready to go toe toe with extra ammo. This would also cause a higher probability of no later retaliation because I  intervened. I also would not be showing my full hand either, as my AR and shitload of 30s and 20s already loaded up inside should they be foolish to came back later. A 911 call would waste too much time.