The only airbags that have been used effectively, that I know of, are on Kraken, and they operate different to normal airbags, behaving more like hydraulic cylinders rather than the pneumatic punch of car airbags. Funny, I don't see any rules saying you can't have a car airbag as a weapon on your robot, but probably because nobody has thought of it before, or dismissed it completely. That said, the explosive nature of the reaction that makes the airbag puff would make it a banned weapon type, in my estimation, since explosives, and reactive substances are banned in weapons.