Revolver. Like to get an AR or similar sometime soon. Maybe this summer. I'm somewhat suspicious of the remarks indicating that .223 is unique in the world as a magic bullet, though. Penetrates body armor easily, but fragments when it hits flesh, never goes through too many walls, but it can go through steel plate like butter... sometimes the AR afficianados come off sounding like marketers for Extreme Shock.
As for overpenetration of walls, we'll say that .45 ACP FMJ goes through 20 sheets of drywall... .223 (of what make and model, couldn't say) will go through around 15 sheets. Still going through multiple walls, but not so many as handgun rounds will. Those numbers are made up, FYI - but the real ones are somewhat similar. The .223 round will go through several walls, but the lower-speed, heavier-weight handguns will go through more walls.
Since HD distances for me = spitting distance or closer, thanks to size... well, Ray Charles could point-shoot in my place. And hit the BG every time.