Answer:
What invention lets you look right through a wall?
I hop around and deliver eggs at Easter.
Who makes it, has no need of it. Who buys it, has no use for it. Who uses it, can't see it. What is it?
The more you take the more you leave behind. What are they?
I march before armies, a thousand salute me. My fall can bring victory, but no one would shoot me. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.