One feature of the microbit I haven't explored too much in the past was the music module. This module lets you play simple tunes using a dsl for pitches, octaves and durations (and, of course, rests). You can read the details of the API here.

I thought it would be fun to write a program to play Jonathan Coulton's end theme from the game Portal.

from microbit import *
import music

still_alive = [ 
    # this was a tri
    "R:4", "g6:1", "f#", "e", "e", 
    # umph
    "f#:4", "R:4",
    # I'm making a note 
    "R:2", "R:1", "a5:1", "g6", "f#:1", "e", "e:2", 
    # here Huge Success	
    "f#:3", "d:2", "e:1", "a5:5", 
    # it's 
    "R:3", "a:1", 
    # hard to overstate 
    "e6:2", "f#:1", "g:3", "e:1", "c#:2", 
    # my satisfact
    "d:3", "e:2", "a5:3", 
    # tion
    "f#6:3", "R:4", 
    # aperture science
    "R:4", "g:1", "f#", "e", "e", 
    "f#:4", "R:4",
    # we do what we must
    "R:2", "R:1", "a5:1", "g6", "f#:1", "e", "e:3", 
    # because we can
    "f#:1", "d:3", "e:1", "a5:5", 
    "R:4", 
    # for the good of all 
    "e6:2", "f#:1", "g:3", "e:1", "c#:3", 
    # of us except for the
    "d:1", "e:2", "a5:1", "d6", "e", 
    # ones who are dead. But theres
    "f", "e", "d", "c", "R:2", "a5:1", "a#:1", 
    # no sense crying over 
    "c6:2", "f:2", "e:1", "d", "d", "c", 
    # every mistake you just 
    "d:1", "c6:1", "c6:2", "c6:2", "a5:1", "a#:1", 
    # keep on trying till you 
    "c6:2", "f:2", "g:1", "f:1", "e:1", "d:1", 
    # run out of cake and the
    "d:1", "e6:1", "f6:2", "f:2", "g:1", "a:1", 
    # science gets done and you 
    "a#:1", "a#:1", "a:2", "g:2", "f:1", "g:1", 
    # make a neat gun for the 
    "a:1", "a:1", "g:2", "f:2", "d:1", "c:1",
    # people who are still alive
    "d:1", "f", "f", "e:2", "f#:1", "f#:1"
] 

music.set_tempo(bpm=60)
music.play(still_alive)

The challenge was in notating it correctly with the right timings and pitches. Having everything in one list makes it a little bit difficult to maintain and to work out where you are if there is a problem but it does give you a nice compact music format very similar to the sonic pi dsl.