I actually don't use a pedalboard, so I can take pedals on a whim. The three that get the most use which I'd choose (excluding a compressor (either always on on my VB99 or I take an MXR M87 if elsewhere which is nearly as good)
EWS Stormy Bass Drive (Tiny, gritty and cutting)
Meridian Funkulator (Octave, fizz and envelope)
Aguilar Graphe (phaser)