What Am I Riddles

Question: Silent yet deafening. Invisible, but you know it's there. It can either make you laugh or it can make you cry. What is it?

Question: Without me, nothing exists. What am I?

Question: What is often picked but seldom chosen, never walks but can run when frozen?

Question: I don't like crackers and I don't drink tea. I just want to eat what I used to be.

Question: I shoot people and sometimes cut off their heads. What am I?