Plimsoul & OCD
MXR Custom Modified Badass Overdrive & MXR 78 Badass Distortion
Boss SD-1 & OCD (I argued about this one, but they do marry pretty well. I don't use it regularly, but it works.)
The problem I have with any and all stacking is that it gets very noisy, to the point where you only really want to have both pedals on for a short time. But certain settings where I mix the Plimsoul & OCD are really awesome.