For my husbands 40th I wanted to do something spectacular. However I did not want to do the typical "over the hill" theme.  I decided to do a scavenger hunt.  All the guests received their invitation on a cassette, which said " you have been selected to perform an impossible task. If you choose to perform this task please be at (our address) on (date ) at ( time) and that is where you will receive the next step for your task.  Once all the guests arrived they were put into their team (4 adults per team) and the rules where explained. They were given their list of items to find. With each item that was found they had to take a picture with three of the team players and that item.  (this kept the team from splitting up)  once they were all done with finding their items they than had to go to one hour developing and  develop their photos for the proof. The first team back won. They all returned to our home with tired feet, great stories and a lot of memories. My husband and I had the grill going and fed our hungry agents. During dinner we than presented everyone wtih a great gift for participating and everyone went home happy. This was a twist on the typical party because our guests were the focus and watching them enjoy themselves made far better memories than everyone watching the birthday man.