On a budget, the Big Muff is the fuzz to get. It sounds awesome, it's easy to use and cheap, and it has enough distortion for anybody.
Not on a budget, look for a used Foxx pedal (fuzz, fuzz.volume, fuzz/volume/wah, or fuzz volume/wah/octave are the usual cominations) on eBay. Though it will run you about 300$, there is nothing heavier.