Invite a guest to come share an experience with a gospel topic with the class. Listen during sacrament meeting, Sunday School, and other times to find people who have experiences or testimony that is valuable to share with your students.
I've had great success doing this, especially when I take the time to explain the purpose of my lesson to the guest. "We're having a lesson on missionary work; would you speak?" isn't clear enough. "We are studying the scripture Jeremiah 16:16. Would you come to my class next Sunday during the third hour and share a mission experience about hunting people out of the holes in the rocks with our class? Is 15 minutes enough time?" is much better.