Overtone GEQ

Simple, quick and very effective.

An important thing that may be easy to overlook, but is really the reason why I like this EQ so much:
The frequency of each band can be adjusted freely by clicking/dragging the numbers above.

In my opinion, that's what makes it occupy the sweet spot between flexibility and simplicity.
It's an intuitive and powerful tone shaping device, yet there is nothing that distracts or invites endless tweaking.
I found it especially useful on distorted electric guitar (pre and post distortion) and on synths.

For the things it doesn't do (like high pass), there are lots of other EQs anyway.
For me this EQ wins due to workflow and being great at what it does.