The only example of a target-specific weapon I know is a Kubikiri: a Japanese knife to behead the dead enemy.
Felled knights were usually finished off with a Misericordia. Its thin blade (a spike, actually) was designed to stick it into the seam of sectional armor. The best place was, of course, the neck but one can easily imagine a particularly sadistic victor using... inguinal area as a target. It would be difficult to imagine a warrior carrying a panoply of implements for each particular area of the body: one for the wrist, another for the armpit, yet another one for ... bollocks. Battlefield is not a kitchen where the chef has paring knives, boning knives, slicers, dicers etc.
This is the reason I doubt the theory of the bollock knife being used for a particular function first and appropriately decorated later. Daggers and swords always had somewhat phallic connotations; the addition of ovoid protrusions to the base of the hilt just reinforced the idea.
See:
http://www.answers.com/topic/bollock-dagger