Boss DC2W and Fromel Seraph Deluxe - Always loved Dimension style choruses and this works great with synths, I love it on high/fizzy/airy pad sounds the most.
Moog MiniFooger Drive - Very underappreciated/under the radar device, absolutely NUTS pedal that has clean boost, distorted FET boost/overdrive, the classic transistor ladder filter (with Res), CV input, and another crazy EQ style filter. A huge array of sounds can be had. I like to pair it with my Mood Grandmother doing dirty bass and leads. Insane on electric guitar too.
NOS Germanium FuzzFace - My friend Gael from TouellSkouarn built for me in return for some mastering work, but I only use it when I really want to destroy things!
Eventide H9 Max - Works as well for synths as it does for guitars.
I also have a reamp box from Orchid Electronics permanently hooked up so I can send any balanced line level tracks from the PC through it and into the tube amp or the pedals (or both!)