People who know me know I'm a fan of Joss Whedon's short-lived TV show Firefly. I was thinking about one episode in particular today, titled Out of Gas [Spoiler warning: link goes to plot synopsis]. Their spaceship is dead in the water, er, space. Captain Malcolm "Mal" Reynolds divides the crew into the two short-range shuttles, sending them in different directions in the desperate hope that one will come across help. In case that happens, Mal is staying with the ship so he can call the other shuttle back.
So what does this have to do with UI design? Wash, the ship's pilot, recognizes that Mal will need a way to call the shuttles back, so he comes up with the most user-friendly solution he can think of: he jury-rigs a big red button onto the radio. Mal doesn't have to worry about radio frequencies, tuning, electronic jibber-jabber, etc. He just has to push the giant, red, candy-like button. It's beautiful UI: simple, low mental overhead, no fiddling around necessary.