I have a couple of stompboxes. I don't use them that much. I generally like to set things up and just play. I have a Fuzz Probe, and it is a blast to play with in my opinion. I like making a lot of noise and somehow getting the chaos back to a chorus. The Pixies had that lasting effect on me. But besides dirt boxes, a good wah is probably next on my list. I have a nice one, but wahs are interesting beasts. People tend to be very brand specific about them. I just went with what sounded good to me. I have read that some don't like fuzz pedals, some sound odd with single coils/humbuckers (ie they work well with one rather than the other), some are goofy with noise drops because they are not bypassed properly, and so on. Other than that, a chorus pedal is nice if you play music that has that kinda effect in it. The Boss Chorus CE-2 was one of the first. I think that was the one Andy Summers used for quite a lot of the Police songs. I like that it only has knobs.
Patrick