I'm not too coordinated and paddle ball has never been a great skill for me. I thought an Arduino, assisted by a servo motor and some 3d printed parts, could perform on a par with me. I was not disappointed.
Start by printing the base (which slides onto the end of my glass table) and the rod and servo motor bracket.
Mount the motor to the bracket.
Attach the motor and bracket to the base. I "weld" the PLA pieces together using a low wattage solering iron (it just melts them together).
Affix the rod to the servo motor horn. I used magnet wire, but fishing line would work just as well.
Glue the paddle to the rod assembly (I used super glue gel).
Using pin 7 of the Arduino Uno as the control pin for a servo motor, I installed the sketch "servo.ino" to make it run. The servo is powered by four AA batteries. Negative from the batteries is tied to negative on the Arduino. I powered the Arduino with a 9 volt battery (through V in).
Slide the device onto a glass table and turn it on. If you don't expect it to hit the ball, you won't be disappointed.