Mind Power Games
One lateral thinking puzzle you can try right now involves nine dots, layed out three by three. You have to connect them all with four straight lines, and without lifting the pen or pencil from the paper. Figure this one out and you'll appreciate the expression "thinking outside of the box."
Mind Games For Groups
Some group mind games are especially good for long trips in a car. For example, someone looks out the window and randomly chooses an object. Everyone in the car then tries to imagine a new way to make money with it. Street signs become places to advertise, trees are sold with names, and a truck becomes a traveling grocery store.
The "change of perspective" technique can be used as a problem-solving game. Pick any topic, and see who can come up with the most unique new perspective. Could there be a world where jobs weren't necessary? How would a virus define morality if it was conscious?
Another creative game for a group uses a specific technique, called "concept combination." Simply combine random concepts or things in interesting ways, and see who has the best idea. A chair and a microwave? Maybe an easy-chair with a built-in cooler, microwave and television, or microwavable "couch potatoes" - a potato snack in the shape of a couch.
More Mind Games
Some lateral-thinking puzzles use a scenario, real or imagined, with a selection of things you have to use to accomplish something. Imagine a ping-pong ball in an iron pipe that's set in cement. The pipe sticks up two-feet high, and has almost the same diameter as the ball. With only a box of frosted-flakes, and a t-shirt, how many ways can you find to get the ball out of the pipe? You could also set this up for real, to know if a proposed solution will really work.
Riddles are just mind games or lateral-thinking puzzles. You move laterally in your mind, away from your usual line of thought, to solve a riddle. What did his friends do when the canibal was late for dinner? Gave him the cold shoulder. Keeping your brain in shape doesn't have to be a matter of serious study, does it?