I was having difficulty getting my students to take their Friday spelling test seriously. So, one Friday, after correcting the tests, I passed them back to the students and said that anyone who had a perfect score was allowed to fold the test paper into a paper plane. I then took the entire class to the auditorium--just before lunch so as to avoid a return trip to the classroom--for a flying contest. The three students whose planes flew the farthest were given a simple reward.
Back in the classroom after the flying contest, I announced that they would have another paper plane contest next Friday after the spelling test.
In one week, we went from having 8 students with perfect scores to 24 students with perfect scores.
Ya gotta love it.