Here's a cool dirty reverb effect by Death by Audio. It uses a Belton brick like many other designs, and offers clean reverb with the gain control turned all the way down. But when you increase the gain, fuzz is infused to the signal. You can mount the Belton brick to the board from the solder-side (best to do this once the rest of the board has been populated). It'll probably be too tall with the brick to fit in a 1590B, but a 125B should work just fine.
