For those on two wheels, check out the BDK (Bicycle Defense Kit), offering options for dealing with aggressive motorists. Contained within an altoids tin, the 8 tools vary in detectability, potential to cause damage, and legality.
Specifically, cyclists can:
• Issue "citizen citations" with official-ish tickets.
• Label offending vehicles with an "I was a jerk to a cyclist" sticker.
• Introduce the risk of paint damage with a Jolly Rancher.
• Create certain coating cremation via DOT3 brake fluid.
• Make cars stink worse than their exhaust with a carefully-placed stink bomb.
• Throw a trusty bolt to dent offending traffic as it passes.
• Lock out loony drivers by filling their keyholes with super glue.
• Cut through tire valve stems with a utility blade.
Bicycle Defense Kit for $19.90 at: http://bdk.dirtnail.com