Mark balls with three different colors (dots the size of a penny usually work fine). Assign a signal for each color. For example:

blue - hit away
green - take one
red - bunt

Players must perform the correct action based on the color marking on the ball. Obviously bigger dots make the drill easier and smaller dots make it tougher.

This simulates having to read a pitch, then perform the appropriate action to hit it. For example, seeing and recognizing a change up, then taking the appropriate action to hit it.

You can do this with regular balls, your pitching machine balls, and even wiffle balls. You can us lines around the ball instead of dots (lines are usually easier) to make the drills more appropriate for the age group and/or skill level you are working with.