Last semester I required my students to create three lessons on important course content. By asking the students to take on the role of teacher I raised the bar for their level of understanding on those three topics. The quickest way to discover where a student is faking it is to ask them to explain their understanding of an idea.
I allowed students to select their own topic from among a list of learning objectives. Some students chose a broad approach, while others zoomed in on a specific idea with specific examples. Overall these teaching items were quite popular, and students did a good job. The tasks were fairly open ended so there was lots of room for creativity.