I made a little game and it's been wildly successful getting 2950 hours of combined playtime in the first week and also being featured in Rock Paper Shotgun!
It’s a speed tapping game and its uncontrollably addictive. I am constantly getting people around the office showing me their new high score.
You can get the Android Play Store version: https://play.google.com/store/apps/details?id=co.uk.davetech.twotap
And there is also a browser version you can get here: http://www.davetech.co.uk/twotap