Good Riddles

Question: I always wait unit you're off guard or get older so you can become easier to attack. Once your body is weak, I strike inside you and try to kill you. What am i

Question: I'm made up of 12 completely different letters but you can type me with just 1, what am I?

Question: A man walks into a bar and buys 3 pints in total costing 5 pounds the man leaves the bar wirhout spending a penny. Hows this?

Question: I have a neck but no head, 2 arms but no hands, I go with you to school, I go with you to work. What Am I?

Question: What is something you'll never see again?