Pirates of the...
Host a themed treasure hunt party complete with rival crews of pirates. Purchase or create two beards made out of yarn. One will be blue and the other red. Hand the beards to the "captains" of the pirate crews. The Blue-Beards and Red-Beards will then be given lists of pirate-themed items to find around the vicinity. They must "plunder" the items or take a picture of their team by it. The winning pirate crew gets a chest of chocolate pieces of eight.
Where's Waldo
Have a volunteer dress up like the character Waldo: blue pants, red and white striped long-sleeve shirt, round glasses and white knit hat with red trim. Have this person go to the local mall and sit down in an inconspicuous public place, such as the food court. The treasure hunters must find Waldo and bring him back to the "home base" in order to win the game. The other team will be notified once Waldo is found.
Mind your P's and Q's
For a harder challenge, come up with a list of items that all start with the letters P or Q. Items could include peppercorns, pinecones, pizza, quilts, q-tips, Quaker Oats and quarters. Get creative and encourage guests to dress up according to the theme.
80s Theme
Take advantage of the fact that the 80s are back in vogue. Have people locate things that include Transformers, G.I. Joe, Ghostbusters and My Little Pony. Items could be as simple as action figures or harder-to-find like themed notebooks. Before the party, have guests brainstorm by discussing what they associate with the 80s.