Once your students have mastered the regular IR verbs, "Où sont les trésors cachés? (OUVRIR, DÉCOUVRIR, SORTIR, PARTIR)" will help them to learn the 2 kinds of irregular IR verbs. This activity works well as a full-class, teacher-directed game or as a small group activity. After the fun of the oral treasure hunt, you can also assign co-ordinates to create an instant written assignment to reinforce the correct spelling of the verb endings. You’ll find that even reluctant learners will be motivated to listen carefully and the promise of “treasure” tends to generate enthusiastic oral participation as well. My answer key is for the présent tense but the game works for virtually every verb tense and even the subjunctive mood.