As a 13 year old, I put my first application on the store in October 2009, and all it does is play those mosquito ringtone sounds, and I still make ~$300-400 a month. It always manages to maintain the top 50 Entertainment in some random country.

EDIT: Top 50 Entertainment for iPad, Top 100 for Entertainment for iPhone. I would recommend making your app universal, even if it is just to make the app fill the screen. There is a much smaller pool of silly apps for iPad ;)