chapman stick

if you can't decide which instrument to play, check out the chapman stick, developed by emmett chapman in the 70s. the chapman stick sort of looks like a guitar with a wider and longer fretboard. it has 8 to 12 strings (so you have the range of a guitar and a bass). you play it by tapping it with both hands, so you can play multiple lines at once, performing bass, melody and chord lines simultaneously.
check out these two amazing instruction videos by greg howard: one and two.