I was just looking for a game on the same topic, and I found something called 'Rummy Sentences' that isn't specifically targeting this grammar point but can work for it. Make a bunch of cards with parts of sentences on them (individual words or phrases, including 'will') and give the sets to each group. Each student gets 5 cards to start, and the rest go in the middle shuffled. The first student flips the top card over and either takes it or the top card from the discard pile, and tries to combine it with something in his hand to make a sentence. If he can make a sentence, he lays the cards out in front of him in order. If he can't make a sentence, he discards 1 card from his hand and it's the next player's turn. You can also take add on to another player's already-laid-out sentences with cards from your own hand. Other than that, just make them say the sentences they make out loud, and the first one to have no cards in his hand ends the game, and you give 1 point for every card laid down and take away one point for every card left in the player's hand, and the one with the most points wins.
If you are a JET who has Team Taught Pizza, there is another game called 'English Mastermind' that uses 'will' specificially on page 121-122 of my 2005 edition. It involves giving a pair of kids a worksheet with multiple choices of subject, verb, and object/phrase combinations that they pick one each of to make a sentence, and the other kid has to guess what words their partner chose. For example, if the first kid picks ROB will STUDY ENGLISH NEXT MONTH (3 points, Rob, study English, and next month), the partner has to guess the correct sentence. If they get any part right, it's one point, but they don't get to know which part they guessed correctly (unless they get all 3 right the first time). They have to keep switching things around until they get all 3 points correct, and should manage to do so within about 10 tries at worst.
Sorry if my explanations aren't very good, if you have questions feel free to ask.
