The simplicity of mountaineering gear constantly astounds me. I marvel at the simplicity and elegance of the solutions to the unique problems posed by mountain travel.
2 carabiners
2 single length prussik cords
1 pulley
These 5 items create a pared down c-pulley system for pulling a fallen climber out of a crevasse. Other pieces can be added for more efficient pulling or for a ratcheting system. But these 5 items provide a simple means to solve a difficult problem.

The more I learn, the more I love this sport/hobby/obsession.