Castration based fetishes are the most common, as they are rooted in the body.

Freud theorized fetishism was rooted in Castration Anxiety, or the realization that women lacked the phallus, the unconscious would divert this phallic libido to another part of the body.

Yes, in his mind the woman has got a penis, in spite of everything; but this penis is no longer the same as it was before. Something else has taken its place, has been appointed its substitute, as it were, and now inherits the interest which was formerly directed to its predecessor. But this interest suffers an extraordinary increase as well, because the horror of castration has set up a memorial to itself in the creation of this substitute.

-Fetishism, Sigmund Freud