One of my best friends from high school plays guitar for Taylor Swift. I'm going to assume that makes me at least semi-cool for being friends with him. Otherwise, I hate guitar players. Always like, hey I play the guitar, look at me. Hey girls, I play the guitar wanna hear a green day song I learned. No....ok that's cool.
I'm pretty sure the coolest instrument one could play is the harmonica, as you can carry it in your pocket and whip it out at opportune times.