What you need: Any gun or a lighter
1. When the invader comes in, get your gun/lighter and burn the lighter/shoot gun in invader's face. Then kick them in the crotch/head
step one: fly a confederate flag (or a "dont tread on me" flag if your not racist). this shows the would be robber that not only are you packing heat, your probably cleaning your shotgun right now =D
You can actually prevent invasions by keeping the porch light on as the intruder may feel paranoid a neighboor could see him and call 911.
Also get those fake security cameras.