Shit, man. Tricky. I'll go for languages- You only need to know one or two instruments to make things what sound good, but knowing every language would give you so much understanding of the meaning and origin of words, and let you go so many places and meet so many people. Like, think of how employable you'd be, as compared to a musician who can play a wide variety of instruments.

An eye on your forehead or missing a leg?