My first instinct was to say "Guitar, duh!" because I'm practically holding one everywhere I go.
But then I thought about it some more, and I realised that if I could choose any instrument, regardless of whether I can play it or not, it would definitely have to be the saxophone.
It's jazzy, it's classy, and it's very, very sexy.
Jasmine Chan Sze-wing, 13, St Rose of Lima's College
I'd play the guitar. My favourite singer, Taylor Swift, plays the guitar very well and her music has inspired me.
I have learned not to be mean to others from her song Mean. I wish I could play the guitar in a band and impress people with my music, as Taylor does.
I believe that music is without boundaries.
Eugene Wong Jun-yen, 18, PAOC Ka Chi Secondary School
I would choose to play drums. Although drummers aren't in the spotlight like lead singers or lead guitarists, they are a vital part of a band.
The drum kit is like the human heart: its beat brings life to music through rhythm.
That is why I am fascinated by this instrument.
Joe Cheng Ka-lok, 16, Sheng Kung Hui Tsang Shiu Tim Secondary School
Being a shy person, I dislike performing. Still, I love singing pop songs as they can express my deepest feelings to others. Whether I feel happy or sad, singing is the best way for me to express myself. Besides, I'm not good at playing musical instruments. So I'd choose the microphone as my instrument.
Catherine Wang, 12, Chinese International School
I would definitely dominate the drum kit. With all the vocals and techno sound effects out there, people tend to forget about the source of the steady rhythm behind the melodies.
Without a skilful drummer, band members would have no way to keep the rhythm together. They would mess up and clash horribly.
Nanor Wong Si-yee, 17, St Margaret's Co-educational English Secondary School
I would be the backing singer. I really like the vocal "instrument" because you can produce so many different sounds with it. Also, the backing vocalist complements the lead vocals with "oohs", "ahhs" and harmonising.
Conveniently, the vocal instrument can be played at many places where most other instruments can't ... such as in the shower.
Rosemarie Ho, 15, Baptist Lui Ming Choi Secondary School
Definitely the bass. It would be pathetic if a simpleton like me tried to play the main melody, and ruined the whole gig. But, seriously, bass guitarists are awesome.
When something really goes wrong with the song, a bass guitarist can help it get back on track by providing some cool backup beats.