We've learned a new game at our house. It's 4-square tic tac toe. There's more strategy and planning than with regular tic tac toe and we are really into it.
Instead of working with a 3x3 grid, you have a 4x4. You are still using two players; X and O. Play is like regular tic tac toe except that players can win three ways: 4 corners, 4 in a square (anywhere on the board) or 4 in a row (vertical, horizontal, diagonal).