One of the highlights of my trip to Wisconsin was playing in the largest game of Werewolves of Millers Hollow I've ever played.
We ended up having nineteen people in one game.
Werewolves of Millers Hollow is the greatest party game ever. It is the hands down favorite amongst our friends. If you've ever played Mafia, it's the same game only with werewolves (thus better).
The group is divided into Townspeople and Werewolves. The Werewolves kill one townsperson each night. The next morning the Townspeople debate and eventually execute one Townsperson they suspect of being a werewolf. The game becomes a race for the town to find all of the werewolves before the wolves murder everyone in the town.
This version is our personal favorite but you can also find versions called "Are You a Werewolf?" and "Lupus in Tabula." I highly recommend it if you ever have minimum of eight people at your house.