This video gets students to make sentences using "will":
http://www.youtube.com/watch?v=cSpty_78cOAThere are 10 short clips, each interrupted with a question ("What will happen?", "What will the cat do?", etc.). Stop the video there and get the students to make guesses. And then when you've gotten some "will" sentences out of them, you can get the class to ask the question together, and when they ask, they can see the rest of the clip.
I've found that these videos are fun enough that sometimes students are motivated to make guesses outside of their English range, but they can usually make themselves clear enough (my earlier experience with this is a series of clips for the phrase "going to", basically the same setup).
Odds are they will all be totally and completely wrong, but if a student's guess is even remotely close, I give them a piece of chocolate. And actually, all the wrong guesses add to the suspense, and the kids enjoy the unexpected endings even more than if they hadn't had a chance to speculate beforehand.