Definitely the forehand. I like to dominate points with it. Jerking the opponent around until I get a chance on a short ball, forehand approach, and volley/overhead.
I can pull it short angle cross court, crush it down the line, or any other spin/flat/deep in court combination. Not to mention my powerful and accurate returns and passing shots.
Alas, my backhand possess none of these qualities. And my serve? Well, for my game, the serve giveth, and the serve taketh away.
So my answer is my forehand