Perhaps a little late for Halloween, but you can use this modded Mario costume for inspiration and get to work on yours for next year. Certain motions while wearing the suit trigger fireball, jumping and 1Up sounds, among others.
The get-up was built by an Adafruit Wave Shield user, connecting the gadget to an Arduino system. I know none of what that means, really, but it allows for the motion-activated sounds. And the soundtrack of course is customizable. So you can bet your bippy someone's dreaming up a Mega Man version as we speak.