First things first, the EHX Big Muff PI is a MASSIVE pedal! Having never owned one or seen one up close I was very surprised at the sheer size of the thing when it first arrived!
Don't let the giant size of the pedal put you off though, the Big Muff PI is a fantastic sounding fuzz pedal, used on countless classic records, and is a worthy addition to any pedalboard! If it's size is a concern, It's also available in a variety of smaller sizes.
The Big Muff sound is a heavily distorted, but warm and creamy fuzz, defined by its signature long sustained notes, which are often described as being 'violin-like'. It's an excellent pedal for both lead guitar and rhythm guitar and can even sound especially dirty on bass!
The pedal lacks any extensive features, opting for 3 knobs to control the extent of the Big Muff's fuzz. You may not have huge amounts of control, but the Tone and Sustain knobs provide the user with a simple way of sculpting rich, dirty tones. There are newer fuzz boxes on the market with more features, but in my opion the Big Muff doesn't need extra options to overcomplicate it's sound and design!
EHX's Big Muff PI is a fantastic pedal, with a rich heritage in guitar music. Every player should get one.