A point of vulnerability.

A sore toe, generally an ingrown toenail, which is a huge weakness to the owner. In any fight, if someone steps on your Achilles Toe, you've lost.

A tendon in your foot right above your ankle.
Vital nerve for moving your foot and standing

A book written by Madeline Miller that is written from the point of view of Patroclus, a close friend and lover of the famous Achilles. The book made many people sob their eyes out and educated them, since Miller did extensive historical research for the book. It's a very well-written book and is a favorite to millions.

Goblin that hides under bleachers or any other object that leaves a space for your heel and slices the tendon on your heel

This is a dick that you can never say no to, because you find it so amazing, and therefore it is your biggest weakness regarding sex. An Achilles dick can be a major temptation whether you are single or already in a committed relationship.

The act of accidentally ejaculating on one's own shoulder. As a result, the embarassing cleanup cripples the man much like the famous greek hero Achille.