Answer:
What has three ways out and just one way in?
A dagger thrust at my own heart, dictates the way I'm swayed. Left I stand, and right I yield, to the twisting of the blade.
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
I am the tool, for inspiring many. Buy me in the store, for not much more than a penny. Don't overuse me, or my usefulness will go.
Without this, eating food and Steven Spielberg's career would be very different.
How do you know if a sniper likes you?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?