OK. We all know it's a great way to boost a signal for a solo. Or to add tone. Even change the sound of your guitar.
Here's some other great uses.
A volume controller.
I have an all tube Fender Champ. Even at it's lowest settings this amp is loud. I also have a Marshall with the same problem. It has a touchy volume knob that can get loud quickly. So I can use my volume slider on the graphic eq to quiet my amps down for nighttime playing. Still have a great sound. Just a lot quieter.
A distortion pedal.
Doesn't matter if your amp is tube or solid state. Crank the volume up on your EQ pedal and you overdrive your amps preamp. With the added bonus of being able to dial in a great tone. Not just one or two 'tone' knobs.
A "Make my distortion pedal better" pedal.
What a lot of overdrive and distortion pedals lack is a good EQ. Some even have passive tones that do no different than the tone knob on your guitar. So if you like your distortion or overdrive sound but not it's tone this is the perfect cure. I have an Electro Harmonix 'Soul Food'. It's a Klon clone. Has a real smooth distortion. But all the tone of a cardboard box. Putting a graphic eq after it made all the difference. Try yours before or after your distortion box.
The "I have tone controls on every pedal I use" fixer pedal.
There are pedals out there that suck the tone right out. Those expensive 'transparent' pedals, when on, can do the same. Easy fix with a graphic eq pedal.
By itself a graphic eq pedal can be your distortion, tone and sound changer. Giving you tone versatility even with one CBG with a piezo.
been meaning to get one to boost and shape the output on acoustics with soundhole pickups. You can get Behringer and Artec ones for very little money
Clapton has used one for years. It’s a good cure to a flat sounding amp, sometimes pedals or piezos can scoop those mids out to deep.