I am still searching for a mild overdrive that I really can say is my favourite; I find they vary so much depending on what bass goes into them. Particularly struggle with active basses.
Heavy drive/distortion, B7K. Fuzz, my custom Cog pedal has a modified Grand Tarkin circuit which just sounds fantastic.
It's a completely subjective thing, and will vary depending on playing style, context and just general personal preference. I suspect they will all be named here