Without question focus on your other interests and skills... be it sports/hobby etc.
If it is in a field outside of the typical domain of these kind of projects it automatically gets a better mark because there is an implicit effect of the marker over estimating the complexity because he/she is not so familiar with the domain.
There is also one special category, if you have good maths skills your project will automatically seem better than the coding effort put into it because of the additional complexity. E.g. it is not much effort to code up a simple electric circuit modeler , if you are comfortable with complex numbers and differential operators. The key element here is that you already have paid the cost of learning the maths skill and you are getting double payback, first of the original maths class and second for the coding project.