To my eye the things I find beautiful are bound up with purpose and execution. The C-130 cargo plane is one example. The original design was made before I was born, yet descendants of the design are still in service. This all makes perfect sense. Propellers are more efficient than jets, and turbines are more reliable than internal combustion engines. Given a decent wing and a clean enclosure for cargo (the fuselage) – there just is not a lot of room for improvement, so the design is still in service.
An elegant and fitting solution to a particular class of problem.