I had to think about this one for a while cause I've been thinking so much about my ocs over the canon characters BUT I will do my best. Sorry if these answers arent in depth, feel free to ask follow ups if you aren't sure about something

Scout - FEET idk what else scout would be into tbh
Soldier - Puppy play
Pyro - Rubber/latex
Demoman - Decapitation/blood in general.
Heavy - I have no idea, this is my fault cause I don't think about Heavy enough aajkgdlkj
Engineer - Objectophilia
Sniper - Filth in general
Medic - Medfet obv, surgery gets him goin
Spy - Stalking