I have found that nothing seems to get people's attention to their brakes faster than having a big extension hitch in my tow bar receiver with a 2" chrome ball attached. Sits about 8 inches behind the street rods bumper and gives the impression of being a radiator killer.

My rear bumper consists of a custom aluminum tube about 4 feet long and 2.5 inches in diameter. Nice to know it's there, don't think it will do much good except maybe hit me in the head during impact thereby reducing the likelihood of lingering pain.