This party requires planning but is great for amateur sleuths!  Guests    are divided into teams and given coded messages for each challenge. You    can make the messages by using an alphabet code.  You can have a message that is written backwards (do this on your computer and use the horizontal flip command) that the players have to hold up to a mirror to read.  You can make a clue and then cut the pieces into different shapes, so players have to put the pieces together to read the clue.  Print a clue on white paper with white crayon so players have to color the paper in with the side edge of a black pencil for the clue to appear.   Make a picture-gram where they have to guess the meaning of the words to solve the puzzle.  Do a fill in the blanks or use a number clue, where each number (1-26) represents a letter of the alphabet.  Use rhymes or clues that make them figure out the meaning.

You can hold this party in a home, school, mall, etc.  The clues should lead to a new area where the team gets their next clue.  Some tasks should involve finding hidden items, or writing down letters or words on their master sheet to complete the challenge.  Set a time limit and an area for teams to come back with their master sheets.  Prizes could be for first finished or most challenges completed.