This year the boys wanted to be Mario and Luigi. Kind of boring right? Well my wife didn't think they were ready for throwing real fireballs so we did sound effects instead. I wanted them to make the Mario jump sound when they jumped and be able to make the fireball sound too and maybe a few others. So I too a Wii Nunchuck, an arduino, a set of portable speakers and a birthday card to make this.
The Wii Nunchuck has an accelerometer in it so I used that to tell when they jump and for them to control the rest of the sounds. The Nunchuck is connected to the arduino using an adapter that you can make or buy so you don't have to cut the cable.
For the sound recording and playback I found a birthday card that you can record 4 sounds on and playback the sounds by pressing each button. After tearing the card apart I found that it ran on a 3V battery so I used an arduino pro mini 3.3V for one and an arduino FIO which is also 3.3V for the other. This way the arduino could directly control the sound board and power it too.