Wow. So few people know what they're talking about...
Non-military uses for firearms (Non-exclusive)
1. Hobby
2. Personal defense vs. crime
3. Home defense vs. burglary
4. Police
5. Hunting
6. Paranoia/Gov't defense
For 1, anyting goes. For 2, you need something concealed. For 3, a 12-gage shotgun is ideal.
I don't trust any police officer who says he's shot people on duty enough to be able to talk about 4.
For 5, Shotgun/rifle, caliber to taste.
It's at 6 where you hit the sticking point. Personally, based on the four current and former members of the US Armed Forces in my family, I think that peashooters would work just fine. The military would rapidly run out of officers who ordered soldiers to shoot at US civilians, and the remaining ones would be loyal to the country, as opposed to the government.
Grenade, because I can still buy duct tape, nails, 12" long 2" thread pipe nipples, end caps, and some common household chemicals.