Atemi is Art of attacking Vulnerable Points. With Weapon such as Knife, or with Unarmed Martial Art Style.
There are many vulnerable points that can be attacked, but i know only of few.
2. Nose Center,
3. Below Nose, (different attack vector than nose center),
4. Lower parts of face - center, left, right,
8. Solar Plexus,
12. Inner sides of Elbows,
16. Slightly above Knees,
17. Slightly below Knees,
18. Where Thighs join with Hips.