A large seating area, chairs for every person plus one more, a hat or container to put names into, paper & pen, a couch or a bench.
Get four guys or four girls on the couch.
Have everyone write their name down on a piece of paper. Put the pieces of paper into a hat and mix them up. Go around the circle making sure everyone recieves a paper with a name on it. Everyone gathers in the circle and sits down on their chairs, with an empty chair beside one person. There must be two guys and two girls on the couch at the start of the game. The person to the right of the empty chair calls out a name and whoever has that name on their paper goes and sits in the empty chair. Those two people then exchange names (papers). The next person who is at the right of the chair that is now empty calls a name, but cannot call the name that was just previously called, they must choose another name. Try to get either the two guys or the two girls off the couch, and then get all four spaces on the couch filled with guys or filled with girls. The game ends when there are four guys or four girls on the couch.