Question

A man drops a baseball off of the top of the Empire State Building. If the action force is the Earth pulling on the ball, then what is the reaction force?

Answer 1

Nitro5315 is spot on.  And the reason the ball "falls down" to the ground but the Earth doesn't seem to "fall up" to meet the ball is because the Earth's mass is so much larger than the ball.  Nevertheless the Earth does in fact accelerate a little bit upward.

Answer 2

Reaction force is the ball pulling up on the Earth. Every action has an equal and opposite reaction, so when the Earth pulls on the baseball, the baseball pulls back on the Earth with equal force