The three or four cell mag would be good, albiet a short reach self defence tool (i.e. weapon) and very easy to explain to local law enforcement. When responding to this I was kinda thinking self defence via "harmless" items. For example, in Great Britton it would be hard to justify the cold steal polymer bats....easier to explain a normal one. Or even better a cricket bat. Bonus of being shorter and heavier than a baseball bat. Other items could be a hammer, either end but steer away from the claw end (asuming you want less than lethal aplications), hatchet, axe or crowbar. Put a couple rolls of quarter into a "double bagged" pair of socks. Kitchen knives, meat cleaver, large pair of sicisors, golf clubs, hockey stick, tennis racket......the list goes on and on.
For me, I'll stick to my mossberg 590 (and yes it does have the bayonet lug...and bayonet) or my glock 22 with nite sights and m3 flashlight underneath.
But I didn't have guns, I'm swinging for the bleacher on the first crook who tries to steal home

-Bill Liptak