We use those plastic practice golf balls. Sometimes we Tee them up all over the yard, or if feeling lazy and the lawn is mowed, I just toss 'em all over the yard.
those, along with a few scattered milk jugs, are great wanderingtargets for judo points. When you get a solid hit on a golf ball, it takes flight across the yard.
Another one is 2 liter soda bottles. Shoot at the cap.
you'll be amazed how fast shooting small targets will tighten up your form, and your groups.
You'll find if you are missing the golf balls, its within an inch. Which is pretty good shooting for randome targets at random distances.