Easy Games
Host a funniest-costume contest for adults at your party. When sending out invitations, tell guests to show up in their funniest costume. Select three adults to vote on the costumes, or have everyone at the party vote. Give prizes for the funniest homemade and funniest store-bought costume. You can also hand out small pumpkins and art supplies such markers, paint and rhinestones; guests can use the materials to create funny pumpkins.
Messy Games
Some adults will enjoy getting their hands a little dirty for a party game. Fill two large buckets with gelatin, oil, cooked spaghetti noodles and plastic body parts. Plastic body parts, such as fingers, ears, eyes, hearts and tongues, are available at most Halloween stores. Put a few decoy items, such as penne pasta, peeled grapes and peeled lemons, in each bucket. Blindfold each player before starting the game. Players must use their hands to dig in the buckets and find three body parts. The first to find three body parts wins the game. Alternatively, use plastic swimming pools and have the guests dive right in to find the parts.
Indoor Games
Funny Halloween question games are perfect for a group of adults. Before the party, write down several questions. Some ideas include, "What is the funniest trick you have ever played on someone at Halloween?" and "What is your most embarrassing Halloween moment?" Assign funny answers one point and extremely funny answers with two points; the adult with the most points at the end of the game wins. Guest can also play charades using Halloween-themed items like a witch, bat, monster and a ghost. Other charade ideas include Halloween movies and television shows like "Nightmare on Elm Street" and "The Addams Family."
Outdoor Games
Hang several doughnuts from a clothesline or string and make sure they
are at mouth level for the adults. With their hands tied behind their backs, guests can race to see who can eat a doughnut from fastest. Make the game messy by using an apple covered with whipped cream -- the first player to take a bite of an apple wins the game.