The Browning M-2 (Forever Young)

Developed in the 1920's, it's still going strong today.

Three years ago, the U.S. Army gave up on getting a replacement for the nearly century old M2 machine-gun, at least not anytime soon. However, many of the current ones were wearing out, so the army began replacing over 80 percent of its 36,600 M2 machine-guns, a process expected to take five years, with new M2s. Numerous efforts to develop a replacement for the M2 have failed so far.

Not bad for a weapon system that is approaching it's 100th birthday. How many things can you think of that were designed in the 1920's that haven't been improved upon since?

[H/T Ace]