Personally id go with either the great big 'fit your whole head in its mouth' Psycho mutt. I know if I was a thieving tow-rag, I would brown it if I came face to face with teeth and drool. Alternatively, fashion some sort of tripwire affair out of fishing line, one end fixed, the other leading to your bedroom window, where it is attached to lots of empty beer cans. If the cans rattle in the middle of the night, introduce the culprits to your new nine-iron or if you prefer your 2x4 with rusty nails.
Whilst on the fishing line one, one of my mates had his shed (of the garden verity, not a Vauxhall) broken into several times. He came up with the idea if three lengths of fishing line across the door, two at face height, and one at balls height. Each line had 10 triple hooks (look like mini grappling hooks as seen on spy films) fixes at intervals along each line.
The shed got broken into again, but nothing disappeared except the three lines. Never had a problem since.
You could think about razors under the door handles. or secret kill switches, or make some kind of second key setup, or take off dizzy cap ant leads at night, or just unplug it.
I know, hire the local nutjob to 'exchange pleasantries' with him (pull his arms off and ram them where only the best of proctologists could reach).
Ahh the posibilities are endless.
ive had someone like that, was parked outside of somewhere, my engine was running and some guy walked past and said he had temptations.... was very dodgy 
