I loved Josh Griffin's "Facebook Hack" game idea that he shared on his blog a few months ago. It inspired me to not only play that game with students but I ended up creating another game as well... "The Facebook Stalker" game.
The idea I had behind this game was really two-fold. I wanted to leverage Social Media a little bit more and encourage students to share with their friends via mobile updates to their Facebooks that they were at church (at our event), but I also wanted to have a fun (and engaging) crowd game to play during our time together. We encouraged our students early in the evening to update their statuses saying they were at our event (you could do this with a simple slide on the screen too) and then later in the evening we had our media tech pull up random Facebook accounts (from random students we selected ahead of time) on the screen LIVE during our event!
If the student had updated their status (prior to our playing the game) to reflect that they were at our church event they won a prize. If they didn't they were a big fat loser!
This Facebook game was a win... and students loved it!