Ditto on the aspirins - we tape them onto black cardstock poster board. The first time I was introduced to this, I got my clock cleaned by a twelve year old boy! 'Course, he had been shooting competitively since he was nine, and Daddy had built him a very nice Ruger 10-22 comp rifle. My old Marlin 60 was NO competition for him! Hehehe......
Potatoes against the back berm - explode nicely when hit!
12 gauge empties - hit them just right and they SPIN up into the air! Cool!
Soda cans on the 110 yard berm was pretty easy - the soda bottle caps were much more fun and challenging!
We use the bright yellow foam practice golfballs - start close with .22 pistols, then transition to rifles when they get out further! They don't fly as far as real golfballs when hit - you get more whacks before having to go bring them back!
The white 'wedding cookies' on the berm - great fun - and biodegradable too!