I have one funny thought about Rubik's Money Bank / Gift Cube:
it is nice idea - when you solve cube, you can open it. It's
not too hard to solve 3x3x3 Rubik's cube. On the other hand,
if you take Rubik's cube without stickers, it will be pretty
easy to solve it: no moves at all, but if you take Gift cube
without stickers and scramble it, it will be extremely
impossible to solve and open it.