We had several favorites.
One annual event was Canadian Thanksgiving. We'd wanted to celebrate T-giving with the kids, but they were always with their family. So we decided to celebrate Canadian t-giving in October. We had all the traditional trimmings, and the kids loved it.
Two totally fun and totally aspiritual games we liked were Newspaper Wars and Grape Spitting. We collected newspaper from the congregation for weeks, and each kid was handed a roll of masking tape and a bunch of paper. With it they had to make shields and swords. Then we turned them loose to attack each other. The last one with an intact shield won the the game. Grape Spitting was just what it sounds - we'd see who could spit a grape the farthest. It was actually hysterical to watch the prissy girls out-spitting the boys!
Be careful with service projects. At our congregation, the adults have a tendency to push all the work off on the teens while they sit around and gab. This doesn't go over very well. If you have service projects, it's a good idea to have adults working side-by-side with the teens.