When I see scifi flicks from the 1960s and 70s, I always love the blocky, blinky lights on all the computers. Though they were obviously considered "futuristic" at some point before we all started fetishizing miniaturization and gesture-based computers. But now the DiY geeks over at Hackaday have found a way to make those blinky blocks into something useful: a keypad combination lock. Instead of keying a number sequence into it, you can key a color sequence. It's a great home electronics project, and it makes your front door look like it should open with that Star Trek "fffwwp!" noise.
Here's how it works: When you press each key, it cycles through three colors. You press the color you want. When you've got your color pattern set, all the lights flash green and the door opens. Obviously, if you want to be safe, you'll want to figure out a way to shield the keypad while you're unlocking it (this is a good idea with number-based keypads too).
You can go through all the steps to make this lock, from circuit boards to LEDs, or you can buy a pre-made keypad here. You'll still have to program it, though!
How to Make an RGB combination door lock [via Hackaday]