My sister and I would have WWE style pillow fights on the bed. All it took to start up the brawl was throwing a pillow at the other for them to defend with and charging with your own pillow yelling "PILLOW FIGHT!" Then we would jump on the bed and and whoever got knocked off first, lost, but that of course did not stop the fighting there. Hallway runs through the house, grabbing the parent's throw pillows (pun intended), escalating to couch cushions, all sorts of sillyness.
Another game I played with my friends. We turned all the lights off downstairs and chuck those giant exercise balls through the pitch dark in random directions trying to hit each other. The fear, the anticipation, and the sound of the ball whistling through the dark. The game had only downsides, but was totally worth it.