Out of my own it's either the Whammy or the PolyChorus.
The Whammy I use a ton, for down tuning, and playing chords with a harmonizer (it works great for that with 5ths and 3rds).
but on the other hand I use the stereo PolyChorus almost all the time, as my guitar sound just a hair short of perpetual has a chorus effect on it (stereo if possible)., and if not using it for that, I'm using it as a slapback echo, light duty Ring Mod (Filter Matrix) that brings out a particular note, and in rare cases a Flanger. Between that and the Whammy, I already have most of the sounds I use.
Outside of my own, I'm starting to fall for the Seppuku Sub Octave Synth and WMD Geiger Counter, those will probably be my next 2 pedals, and I love how I can make videogame type sounds with them (like I can my Fuzz Factory). I kind of play a double role in the band as the synth and guitar, as I also do the synth parts on guitar and use effects to get the sound I think will sound good.
