Why not just flash the intruder with a red laser?? I guarantee you everyone knows what that little red light means. Plus it doesn't have to be attached to a gun. Hand held laser pointer gets the point across.

I know this has worked with suspicious vehicles at my house, slowly driving by or stopped. A quick flash across the windshield and they hit the road. FYI I live on a back country road, no reason for idiots to be stopped in front of the house. Especially out of state vans.