Marshall JCM800 in a box.
The now-vintage Marshall black casing pedals are simply put, awesome. The current underdog is the Drive Master which sounds great and juicy yet still affordable.
The EQ stage is extremely wide, offering treble, mid, and bass shaping options and the gain stage goes from clean to a well-driven JCM800 kind of tone and that is also where its magic lies. That pedal combined with a good guitar and power chords is the sound of stadium shows, it is massive.