PLA - cosmetic & glamours stuff (ornaments for the missus, toys, props, anything that doesn’t need “real” strength… multi-color and “silk” decor stuff is all PLA)
PETG - anything that goes in the car, anything where “real strength” is important (shelf brackets), most of my “functional” prints are PETG. Desiccant holders and “hub weights” are all PETG for the higher heat tolerances.
TPU - anything where PETG is “close”, but the part needs more flex (which is highly controllable just by changing walls and infill)… my 5-gallon Jug cap design was TPU as it needed to flex over the “neck” of the jug to form a tight seal. Gaskets and “interfaces” for phone stands to add friction (I loathe a phone stand that moves around when I poke at the screen… so a layer of TPU on the bottom is win).
That’s it so far, never used PC, ABS, or anything more “exotic”.