Atari Punk Console
Atari Punk console is an astable square wave oscillator driving a monostable oscillator that creates a single (square) pulse. – Wikipedia
Ah man this thing is sick!
I present the 555 timer 
A 555 timer basically provides a clocking signal. 
Over time, the signal flips on and off. We can adjust how frequently this happens.
The Atari Punk Console takes advantage of 2 555 timers. In my case, I'm using a 556 timer. Which basically two 555 timers in one IC (integrated circuit).
The first timer oscilates a square wave and its output is divided by the second timer. One knob controls the frequency of the oscillator and the other controls the pulse width.
Here's a good instructable to follow if you want to build your own!
A lot people use altoid tins as cases. I gutted an old netgear switch for mine.