I have previously made triangular boxes from 3 modules and wanted to try out one from a single sheet of paper. And found out Thoki Yenn's triangular box, where both the box and the lid are made from a single sheet of A4 size paper.
I love how economical the box and lid is! The box is made from half the A4 paper and the lid from half a square from the same sheet. The instructions sound quite complex, but making these boxes is actually quite simple.
Model Details:
Model: Triangular Boxes
Creator: Thoki Yenn
Difficulty Level: Low Intermediate
Paper Ratio: A4
Instructions: Erik Demaine