I'm a big fan of rotary speaker effect on both guitar and organ. I love good old Deep Purple and SRV style rotary sounds. I even built a DIY rotating speaker and horn cabinet (1x10" size) once when I was going after the best rotary speaker sounds. I know nothing beats the big old cabinet moving the air but the best thing available is Keeley Rotary pedal. It sounds right. It has all the bells and whistles you want to have. You can change the ramp speed. You can add overdriven tones to it. You can change the balance. And all this is packaged to this regular size pedal with highly usable and intuitive interface.
I have tested many rotary pedals and there have been some really good and some "okay" sounding ones but this Keeley Rotary has exceeded 'em all. I simply love it. It is amazing and makes me just "feel and taste" the sound for hours.
I could list a dozen different rotary pedals I have tried, tested and owned but they all had their quirks and that "zing" factor missing. Keeley Rotary sounds the part, works the part, takes regular power, is very easy to operate and dial in crazy good tones... if you want a tweakable Rotary Speaker in a pedal form, this is your go-to pedal.