What Am I Riddles

Question: Once you are in my sight, you are gone in a flash, and people tend to use me for cash. I am often used as a dire assist, and people often believe that I cause harm, when I am but its catalyst. What am I?

Question: I always murmur but never talk, i always run but never walk, and I have a bed but I don't sleep. What am I?

Question: I never was. Am always to be. No one ever saw me, nor ever will. And yet I am the confidence of all who live and breathe. What am I ?

Question: I give light by night, but not by day, Am wicked but not evil in any way, Wax for the most but always wane, Except when I'm out, I stay the same. What am I?

Question: I am flat, I am sharp; but I cannot hurt you. What am I?