Technically, you can do impact play anywhere on the body, but some places are more suited for deeper sensation than others, and some places are pretty dangerous if you hit too hard. You can cause internal damage, and nobody wants that. Generally, the places on the body with big muscles and lots of flesh are best to hit, while the places with less flesh and more bone or less padding on the organs are not as safe.
This is not meant to be a comprehensive chart, and please consult a BDSM educator AND YOUR PLAY PARTNER for the places their body likes and doesn’t like to have heavy impact. Each person is different, and each impact play tool is different. Use caution and your best judgment and play at your own risk within your negotiated limits. End of disclaimer.