One-off repairs of parts that can't be easily made with hand-tools and a drill press is one of the best use-cases for 3D printers that I've seen.

An early HTML5 game by Dominic Szablewski.

In this talk Rich Hickey makes a distinction between "simple" and "easy" to justify some oft advanced (if rather anti-OOP) software engineering practices: prefer composition, avoid state, try not to mess up your data by wrapping it in objects.