A little bit of a twist on it...but I love masturbating while someone else is driving - especially on longer road trips. I wear dresses and skirts often - and love either pulling my panties to the side, or sliding them down around my ankles - while I take my time slowly getting off.
It drives me wild when we can pull up next to a semi, and the traffic is so light we can drive beside him for a while...waiting for him to look down and see me playing with myself... And when he does...staying there...driving next to him...so that he may watch. Something about it turns me on so, so much...especially when the speed limit lowers, and you have to drive through a small town...
Sometimes the mood just strikes me.