Give each person a puzzle piece to decorate... keeping the edges intact so it can be re-assembled. Use for a lesson on individual worth... how each individual piece is beautiful on its own. But what a masterpiece you get when you put them all together!
Snowball Fight...kids write 3 things about themselves on a sheet of white paper. They do not write their names on the paper. Wad it up and on your command, have a "snowball" (or baseball) fight. At the end of 1 minute, each student grabs the nearest snowball and tries to guess who wrote it. Would be great at the beginning of the year!