This ad about safe driving uses an interesting concept: the eye test. You can use it in a PowerPoint presentation exactly as it is used here: one variable is declining/increasing and visibility of another goes down.
Another use could be some sort of health check: "how well protected is your business?", using a different image that repeats and gets smaller all the time.

If you liked this post, why not subscribe to daily updates about presentation design via email? Just blog posts, no spam, or you can follow Jan on Twitter to never miss a thing.