Possibly of interest for a two-day tournament – I did this at Cakebowl this year. Publish the draw for the first game on the Sunday, then get people to predict the scores in the top 5 games. Obviously I built a spreadsheet to score it – I did 10 points for a correct result, then subtracted 1 for every TD difference for each player.
If you do have a go at the fun metagame, do let me know – publish it on Facebook or Twitter to let others join in too! The big yellow boxes are where the predictions go, and then the Actuals go at the top (I left the Actuals in from the time I used it, for some reason).