I carried a bag of tennis balls in my unit.
Emplace yourself and get silent. LISTEN. Throw a tennis ball at closet or bedroom doors and it startles someone hiding inside. He may shout because of the startle factor, bolt through the door, try and secrete himself further or in very rare cases, come out shooting or shoot from behind the door. The last scenario is probably very unlikely unless the guy is a wanted cop killer or something similar.
Tennis balls are also great for safely knocking on someone's door. Instead of standing in the kill zone in front of the door, stand several feet away, around the corner of the garage or similar. Throw the tennis ball (or two or three) at the door to "knock" then verbalize your usuall "Hello" or "Police" or whatever.
And in a non-gun related mode, tennis balls are great for chasing away pigeons from your roof/eaves. You can't break windows or damage people or livestock with a tennis ball. You probably won't even hit the pigeons. But hit a big, metal air conditioner unit that makes a loud noise, and you'll scare the birds away at least for a few minutes.
Eventually take the old tennis balls to the desert and shoot 'em up...