Photo by Apple
I've just been sold on possibly the most boring-sounding App in the world - a flashlight. However, if you've ever been in a restaurant/airplane/subway with a bored pre-schooler, this is the App you're going to wish you'd downloaded.
MacLight is, well, a light. It also has a campfire option, but quite frankly this is about entertaining a 4-year-old and fake campfire is not nearly as big at this age as "light I can shine in your eyes, on my book, and most importantly, in my baby brother's eyes."
Warning - don't turn on the strobe light option unless you want things to go from entertaining to blinding headache in fifteen seconds.