Brian Henderson had built quite a few car hack projects. He has found that the very popular chips that are used in cheap RC car controllers have an extra unused output. He connects a button onto the remote and buffers the output from the controller on the car to allow him to power the toy gun. He uses a nerf gun for the first hack and an airsoft gun in the second. Both provide a bit of harmless fun. The common chip that is used for lots of RC cars is the 5-Function Remote Controller TX2C ATS302T/RX2C ATS302R (PDF).