Oh, man... what can I say? This is one of these super niche classics that may have limited use, but when you find the use, oh boy. It tells a lot that the likes of Jimmy Page and King Buzzo have had these on their effect chain, and it's safe to say neither of these gentlemen can be described as conventional or subtle players.
This is one sick little noisebox, having both gnarly fuzz and an analog 2 octaves down effect on all the time. You have the level control (having unity gain only when about full clockwise) and the blend control that dictates the balance between octave and fuzz effect: full counter-clockwise you get pretty much only the octave effect, full clockwise there's only the fuzz effect. Simple as that, surficially...
The octave effect is pretty insane even in analog octave standards. Two down, with a guitar pedal, always on... let this just sink in. It's super glitchy sounding, getting you straight into 8-bit Nintendo territory and changing your guitar into a synth bass when fully implemented. Mixed in with the fuzz it gives you very fat tone, aggressive and out there with any one string riff or lead. The fuzz side is also pretty gnarly, giving you classic and singing silicon fuzz with pretty heavy gating, shortening the sustain significantly.
For a two-knob wonder which pretty much has one knob that totally changes the nature of the pedal, your options are limited on a superficial screening. However, it is more versatile than you'd think.Then again, getting this as your foundation pedal pretty much throws you into Jack White territory and that's it. As a spicer-up and with a bit of creativity and curious testing... wow. You may find some surprisingly tones and uses out from it, as I did. As an example, I threw this in the board with a Boss LS-2 Line Selector and with it was able to blend it in my main signal, and the resulting mix of gains was phenomenal.
Blue Box is a pedal I find pretty hard to straight up recommend to anyone, but I also strongly encourage everyone to get it and experiment around if you ever have a chance. It's a sort of curio, but can also be a great spice for your sound.