Answer:
What body part is pronounced as one letter, but written with three, only two different letters are used?
Everyone has me except for a few. You may not be able to identify me but I can always identify you. What am I?
I begin your sentences. What am I?
I hide in a dark tunnel awaiting my time. I can only be released by pulling back. Once released I may do unstoppable damage.
I suck.
You throw me out when you use me and take me in when you are done.