Put a USMC (or equivalent) decal on your door.

Wasp and hornet killer spray.

Five D-cell flashlight in a metal case (Maglight, for instance).

How nasty/mean/violent do you want to be?

Put nails in your baseball bat (assuming it's wooden) and file them to points.

Set a row nails in a 1 x 2 x 24 (inches) very close together (you'll have to drill) so that about an inch sticks out the 1" side -- you're got a steel-toothed comb sword.

Or just buy a sword and learn to use it...having their hand cut off tends to discourage the most audacious gunmen.

Myself, I still prefer a nightstick (wooden truncheon) -- but I know how to use it.