What pedal completes you?
Would probably be my first pedal ever, the EHX Green Russian Big Muff reissue, such a full, bassy, 'Wall-of-Sound' type Fuzz almost my whole Guitar/Bass sound has been shaped around it since the start.
For effects pedals (like for actual effect), probably the MXR Stereo Chorus (the big yellow box), one of the lushest, deepest chorus pedals I've found next to the EXH Small Clone.
I also have a Dunlop JD-4S Rotovibe that I only got recently, basically just a Uni-Vibe inside of a Wah pedal housing so you can adjust the speed with your foot, I use it to speed-adjust that churning, folding, pulsating feedback, kinda like Billy Corgan from the Smashing Pumpkins does.
Probably those three.