See which of your students can memorize the most digits of pi! (I also require my students to memorize the first 10 decimal places as a quiz.) I usually give the winner from each class their own personal pie!
The first page of this document has enough spaces for your students to write the first 480 decimal places of pi.
The second page lists the first 500 decimal places for you to give to your students to study. (There are multiple copies on the page, so cut it before you hand it out.)