Logic gate simulator would be almost trivial to do. I want to be able
to select logic components from a graphical interface, place them on a
grid, connect the inputs  and outputs and see the result. AND gates, OR
gates, etc.

The lemonade stand I remember was written in C-64 BASIC and in short,
you run a lemonade stand and see how much money you can make by selling
lemonade. Variables included weather conditions, and changing supply of
ingredients. Again, probably trivial. I just thought they'd be fun
projects.