I use one of 2 pedals to get my main dirt sound, first is a Myrtle Pedals Corvid Fuzz, it's basically a jumbo tonebender clones with added tone pot, it's a fat and creamy fuzz that I love! Secondly a Tech21 Red Ripper, more bass than I know what to do with, but more of an overdrive circuit with tweaks.
I do layer a few things on top to get most sounds live though. One of the above acts as the base of the sound then I add one or more of the following - Octave, Subdecay Noisebox, EHX MicroSynth and Moog FreqBox... Basically the sound gets as complex harmonically as you like.
For a single pedal option though I think Tech 21 have the right quality to price ratio going on!