I use a RAT. Its killer. I dont really use it for distortion, but more for the tone I get. Set the gain on 1/4, filter on 1/2, volume like 3/4. It boosts highs. Leads sound really nice with this pedal. I couldnt live w/out my RAT!~!
edit: I use it in front of my high gain Marshall tsl100 full stack. With the gain on my amp at around 8