Answer:
I am a type of weapon for SCI-FI characters
Part carbon part water I am poison to the fishes. Many falsely claim my name I am the pause that refreshes.
By Moon or by Sun, I shall be found. Yet, if there's no light around, I am undone. What am I?
I don't live within a house nor do I live without. Most will use me when they come in and again when they go out.
I have feet on my head
When I'm born I fly. When I'm alive I lay. When I'm dead I run.