Piano is the ultimate instrument. Learning it alone will teach you aspects of playing the drums, saxophone, guitar, bass, and help you easily become a music producer. I started out in classical piano lessons when I was four, and have stuck with it since. It is truly incredible what 15 minutes a day on the piano can do for someone.
Not only will you learn Piano, but you will also learn perfect music theory and see it play out underneath your fingers. You will learn to improvise, creating melody, harmony, and rhythm out of thin air. Finding the chords to songs you want to learn will come easily, as you will recognize the patterns having often used them yourself. You will be able to create your own samples with your playing, and the beats you use them in will come more naturally as well.