Folding is something I do, often to stave off boredom. When my students are working on assignments, I get large slabs of time where I need to be there but am not needed, so I bend paper relentlessly:
Folding grids is painstaking, but excellent discipline – accuracy is the key
Triangle-grid (based on 60 degrees) are easy, and a trivial geometrical construction but square grids are also interesting, providing different collapsing options.
Not sure what I will do with these, but they served a purpose.