5 things you can do with an EQ pedal
-adjust eq after an overdrive or distortion to sculpt the overall sound
-bump up 6.4k to get a bit more 'glassy' of a tone
-Use it like a volume booster
-use it like a gain booster
-run it into the effects loop to sculpt the overall sound of not only the pedals, but the distortion channel on the amp as well
-get more "bedroom friendly" volumes without affecting the tone too drastically
Note that this isn't a be all-end all of EQ pedals, and this is demonstrating the Graphic EQ as well... parametric eq's have other tricks they can do too ;)