Enough wisdom in this one to shut down the Internet! As for common tools, I can say that a ball peen or common claw hammer are devastating weapons (having worked on two horrific murders in which that was the weapon) and easily kept around without comment.
Get a commonly available compact pistol (actually get two if possible) and learn to shoot it well and keep it on your person as much as possible (and don't be talking about it). Your mental game and related preparations are much more important than the gun, caliber or ammo. Get your mind and spirit right and keep them right, then quit worrying.