Answer:
I am the ultimate killing machine used not once but TWICE I can be made by humans.
Always in you, sometimes on you. If I surround you, I can kill you. What am I?
I'm a kind of cup that doesn't hold water, but makes a lot of noise repeatedly. What am I?
In all the world none can compare I am a tiny weaver my deadly cloth so silky and fair.
I build up castles. I tear down mountains. I make some men blind, I help others to see. What am I?
When someone uses this acronym, you know you've got to pick up the pace