One of the earlier projects I created with MIT App Inventor is a simple drawing application. You can set up to 14 different background colors and 14 different brush colors. It has a brush width slider so you can manipulate how thick your lines are. It also has a "Clear Canvas" and a "Share Drawing" button for clearing the canvas and saving or sharing the drawing. I am currently attempting to develop an "Undo" button that will erase the last line that was created. Download the app (only works for Android devices)
I also created a simple calculator. It can add, subtract, multiply, divide, raise a number to a power, and find the square root of a number. It has a clear button, a pi button, it can work with decimals, and has a memory system. It doesn't have a limit on number size, but the numbers will go out of sight if the number is too large. I will probably change this in the future, either setting a digit limit or making a way to see the whole number without it going off screen. Download the app (only works for Android devices)
I also created the Online Sequencer app with MIT App Inventor.