Launching tomorrow: what would you design first?

I'm Wade, a mechanical tradesman who built ShapeNook, 3D design made for 3D printing: exact sizes, a fit test for your printer, overhang checks, color 3MF export, and a sentence-to-model AI. It launches here tomorrow.

Question for anyone with a printer: what's the first thing you'd want to design that your current tools make hard? I'm reading every answer.