Battleship game to practice "e to i" stem changing verbs. Can be done in the present or the preterite. Each student needs a copy with 2 boards: one to mark their ships and one to keep track of their guesses against opponent. They say the conjugated verb and figure out where it is based on what verb was used and what subject it was changed to. There are 2 versions - one takes a full page per student and is better if they've never played before (picture examples, more space, etc.) The other is just condensed to save paper. If you cut it in half, each student only needs 1/2 piece of paper. You can also laminate or stick in a sheet protector and use with whiteboard markers.
I usually allow them to do this only orally. But, you can also have them write the conjugation in the boxes that they've guessed or where they put the boats.