Well... I have a severe intolerance for tailgaters. In my many, many hours of solo driving, I've conjured up a few ideas for anti-tailgating devices.
One device would need a trigger button. It's basically tightly-coiled barbed wired packed into a cylindrical housing mounted longitudinally under the car, somewhere behind the rear axle or just behind the bumper. An electronic releasing mechanism opens the cylinder lengthwise like a clam shell, allowing the barbed wire to spring out of the housing. The natural spring-effect of the packed barbed wire makes it expand to the width of a traffic lane in milliseconds, almost fully before it hits the road. The offending car runs over the coiled barbed wire and it hopefully gets tangled in the undercarriage. Treble hooks or even caltrops tied to the barbed wire with cable could be added to ensure entanglement and/or tire damage.
Another device is more of a Mad Max/fiction world device that I call the "Stinger". It's a barbed spike mounted to the frame using the hitch or is mounted like a hitch (bolted to the frame). It has a coil spring setup for cushioning and the stinger is tied to the hitch with about 20' to 30' of heavy cable. Basically, you stomp the brake and the tailgater rear-ends you. There's a shield plate to protect the rear of the car with the stinger in the middle. The shield plate and stinger assembly compress and absorb the impact because of the coil springs. The stinger is secured into a tube with a shear pin that breaks during this impact. Immediately after impact, the offending car will slow because the driver has stomped their brake but you floor the throttle. So, you are now accelerating and the offender is sharply decelerating with the barbed stinger stuck through their front end. The cable is quickly extended so you violently rip the stinger back out of the car, causing further severe damage. The cable part can be left out so that the stinger remains and you either make a clean getaway or stop. That's up to you, but you don't wanna be charged with leaving the scene of an accident so think ahead.
Ok, that's enough ****** for now.