Best hard riddles for teens

What do you throw out when you want to use it, but take in when you don't want to use it?

What has six faces, but does not wear makeup. It also has twenty-one eyes, but cannot see?

You see a boat filled with people. It has not sunk, but when you look again you don't see a single person on the boat. Why?

As small as your thumb, I am light in the air. You may hear me before you see me, but trust that I'm there. What am I?

I am a vehicle. I spell the same when you read me forwards as well as backwards. What Am I?

What tastes better than it smells?

What did the banana do when it heard the ice scream?

What can travel around the world while staying in a corner?

What is unusual about the following words: revive, banana, grammar, voodoo, assess, potato, dresser, uneven?

A man and woman run through a field holding hands. They bound toward the sunset, happy as can be. Suddenly, the man moves off of his straight-line course and starts veering to his left. At the same time, the woman begins running off to her right. They continue this for a full minute, but never let go of each others' hands. How is this possible?