The more you hit it, the stronger it becomes - what is it?

The answer is a nail. Every time you hit a nail with a hammer, it is driven deeper and holds tighter, so the more you strike it the more firmly it stays in place.

A nail is meant to be hammered. Each blow pushes it further into the wood and increases its grip, making the joint stronger - unlike glass or an egg, which would break.

It is a medium logic riddle. The trick is that most objects weaken when struck, so it tests whether you can think of something that benefits from being hit.