Electro Harmonix Bass Big Muff Pi

It's well built, and have usable controls.
The tone knob can do loads of different Muff tones, and doing a fine job at it.

Though, it easily gets lost in a mix, due to the heavily scooped tone this pedal provides, where I rather want to recommend the Deluxe Bass Big Muff, if you're into this tone.
Scooped tones are not really for my tastes, but definitely to someones likings.

Personally I felt this pedal was a bit to fizzy and undefined for my tastes, but you gotta try for your self with your rig to really get the feel of this pedal.

If you're into the Muff thing, definitely try this out, as the price is great, and you'll definitely get Muff tones out of this pedal.