Hit a few floppy disks and hard disks with .25 ACP and 9mm pistols.
On a cadets school visit to the artillery range we fired on a double-decker bus a few miles away, using an ordnance QF 25-pounder, There was only one direct hit and two partials, but as I pulled the string several times, I am claiming the bus
Used 100 sheets of reject X-ray film for a training day. They were punched at the top and suspended from a beam. The sheets could stop any handgun round and also a 12 gauge slug, all fired from 20 feet. Stopped a crossbow bolt also.
As a teenager I made several exploding targets from match boxes, placed them in small tins with about 100ml petrol in the bottom and set those off by air rifle. After the last one set off neighbours' car alarms I stopped doing it.
Had a lot of fun splitting air rifle pellets on scalpel blades also.
Oh, I shot an LCD monitor with a compound crossbow, the arrow did NOT go through, those things are tough!