The most hardcore act of taking a car from point a to point b. The stormtrooper is the person who rides outside of the vehicle because either he/she chose to ride there or all of the car is filled up with people. The person or persons hang on to mirrors, racks, windows, etc. just to stay on the car.
Ben: Hey John, let's take your White Marauder mudding!
John: Ok but I'll be stormtroopering so you will have to drive.
Russell: John! It's raining outside.
Ben: John is a true stormtrooper.
Joseph: Man I wish I could troop storms like John...He's so hardcore.