One of my favorite toys as a child (and yes, even as an adult), is Lego. The bricks are great fun for stress relief and they require at least some amount of imagination. I have sets back from the early 70s all the way to a pristine, in-the-box collection of all of the Harry Potter-related sets (I don't know why I'm keeping them in the box, other than to say I have them... maybe I'd let my kids play with them?).
But the toy villain from my youth has got to be the Rubik's Cube. They musta' released a billion versions of that thing in the 80s. And if 9 squares/side wasn't bad enough in about 10 different sizes (from microscopically small to desk-size large), the 12 square/side version (Rubik's Revenge, I believe it was called) was awful. Then they released them in ball-shaped versions, triangle-shaped versions... even a thing called the snake.
So I'm quite happy to see that someone took the time to build a Lego Mindstorms (computer-controlled Legos) set that is designed to solve a Rubik's Cube. It works by color-reading each side, generating a solution set and executing it. Check it out: