Carrying on the 'white box' theme, here is a Monotoniclabs N37 seq/synth that combines a simple 4 step sequencer with a voltage controlled oscillator for your noise making pleasure. With the clock rate low you get some fab 4 note sequences, turn it up fast and you get into computer game FX-type territory.
Check the guys website here.
From crisp while lines to our favourite yellow box of peril - the Bug Brand ICONweevil. A few years old now I'll leave it to the man behind it's truly chaotic audio madness to explain what goes on under its hood (as taken from the Bug Brand website).
"The sonic-heart of the Weevil is a bank of simple squarewave oscillators that are ring-modulated together to give a large range of sounds from drone to crackle. A range of circuit-bend techniques are then added - power starvation to make the oscillator section spin into chaos modes and body contacts which allow the player to touch parts of the circuit and directly alter the electronic flow."
A much more eloquent way of saying lick your fingers, touch the metal front plate and make it go bllleeepzzzywahhhhhwhhoooosshhhhhzzzzttt!