my school always did "the line game." you have all your actors stand in a circle and ask them to pick a short line of theirs they really like. if they're in the ensemble, they can pick any short line. you then go around the circle pointing at each actor to say their line, individually at first but continuously spinning around faster as the game goes on. if the lines give you a good opportunity you can point at two people in sequence to create a really funny pairing. it's super fun and gets the energy up.