A line rider-esque game, where you draw a line and your little guy goes down the slope (line) you just drew. It can be based on this version of line rider.
This game is not of huge importance. It would just be a fun thing to past time with for O2 owners. It would be usefull for all users who use the O2 for casual purposes, which is the vast majority.
If the notepad app every becomes open source it will help with being able to draw the lines (slope). But it would be also difficult because developers would have to figure out how to make the game have "gravity".