As long as it's attached to a nine-year-old, I'm good.

A smooth pale prepubescent vulva is so cute.

a tightly circumcised guy with a clear circumcision scar

I dunno... Probably a dog knot? I dunno what it is, something about that in particular is just a 'yes', I think it's probably the general shape of it. It may also be the association with dogs, and how rabid they can be while mating.
Other than that, probably the pussy because it seems like it'd be the most fun to tease.

Good question x3 probably dick or ass. I'm a simple dog >w<

Gross warning.

Humanoid cock with excess foreskin and smegma, fat droopy shaft, somewhat discoloured skin, damp and smelly.

do not have a favorite i enjoy it all very much but cloacas are quite fun and i think about them a lot