Every Monday in science, we have "Brainfreeze Monday". Each week, a different kind of puzzle is presented to the students to solve. The objective is to get students to think "outside of the box". They participate in Lateral Thinking, Sudoku, Battleship, Tangrams... the list goes on and on.
The students are placed into groups of 4 or 5. Each group is then given a puzzle to solve. The groups compete against each other to see who can solve the puzzle first. It's something that is fun for the kids, but also something that challenges their brains in different ways.