That extra nip
A bit of reverb or delay goes a long way to bringing out the best in a synth. Here are some of the effects pedals I've spent time with.
Chase bliss audio
An analog delay with digital control - the crunch and dark depth of this pedal can pull some amazing tone from a simple saw or square.
For the modulation section alone, I will never let go of this pedal.
A combo delay-verb with wet controls that will eat your signal whole. A rare stereo guitar pedal that works fantastic with wide pads and any pre-panned or chorus-effected signals.