Back in the '70s, my best friend really hated drivers behind with their brights on. So.....
He filled his trunk with car batteries, and mounted an aircraft landing light in his back seat. We got more than a couple of laughs out of that.
My brother had a friend with one of those devices that can spark unburned fuel form the exhaust pipe and shoot a flame off the back. He was being tailgated one night and the car wouldn’t back off, so he lit the exhaust up and burned all the decals right off the State Police car behind him.