BOSS 7 band EQ-An okay EQ, not really necessary unless you're one of those people who has to have complete control over their tone. Generally used to shape distorted tones, but could be used to cut or accent any frequencies you feel need to be tweaked.
Pro Co RAT2-Good fuzzy distortion. I like it a lot, but mine's been modded by keeley and I've never played a stock one before. Check out Keeley's version. Does tube overdrive to hardcore metal.
Big Muff-A really bassy fuzz, thick and loud, Jack White exemplifies the Big Muff for rhythm guitar. Think Santana and David Gilmore (pink floyd) for it's soloing sound (which is the only thing I use it for).
Ibanez Tube Screamer-Great transparent overdrive (my favorite), look for a TS 808 or a TS 9 modded to 808 specs. Very transparent, meaning it doesn't color your tone, which is only a plus if you have good tone to begin with. I personally love it, it's by no means a heavy distortion, a slight breakup and solid sustain to kind of crunchy is about all you get from it. So if you're looking for a heavy distortion, this is definitely not it, it's the pedal you get for sexy blues solos or to give some rhythm a little dirt without really loosing clarity.
Hope that helps.
What other pedals do you have? If you've already got an overdrive, then I would get the muff, if you've got a fuzz already, get the overdrive or Rat. An EQ is just a good pedal to have around in general, but you probably won't use it as often as the others.
