Around here the police have written so many "vandalized mailbox" reports that they honestly do not mind a bit if you decide to exact revenge. One of my friends used his workplace welding rig and welded two huge pieces of steel pipe together. There was one pipe that was the pole, sunk into the ground with concrete, with rebar going up through the middle. The rebar was bent into a cage around the standard post-office-approved mailbox, and then there was a huge 10" diameter steel pipe welded around the mailbox/rebar contraption. Their neighbor ran into it while driving drunk and totaled her car. Mailbox was fine. Cops reckoned it was her own fault for DUI, so...
DH's trick: Sink two steel pipes into the ground on either side of a basic mailbox/pole setup. Encase the whole thing in a decorative artsy thing with, you know, the nature theme of your choice. When the brats drive by with their baseball bat, they will break either the bat, the car window behind them, or their arms.