Bob, I think it depends hugely on what amp you are playing into, and also whether you are using the amp clean or dirty.
For example, I really like the OCD V3 into a Marshall-type circuit, but not into a Vox Top Boost circuit. I love my MI Audio Blue Boy Deluxe boosting an already dirt amp, or boosting another pedal, but it's generally horrible at providing the dirt into a clean amp.
But in general, some very special pedals that I have really enjoyed are :-
MI Audio Blue Boy Deluxe into a dirty amp
Zvex Box of Rock into a clean Amp
Jetter Gain Stage Red - into a clean or dirty amp
SPF Ego Booster - clean boosting a dirty amp.
All of these are very amp like in their own way, and clean up reasonably with the guitar's volume knob. They also let the sound of your guitar and amp come through, but just enhance it in their own way.
There is such a huge choice of pedals out there at the moment. Sometimes it seems a bit daunting to choose the right one. Good Luck !