Put an apple on your buddy's head. Choose the big head as the other one might be too risky

Cinder block seems like a good idea until you hit it. Pendulum water baloon is cool too. Could try some of the goofy crap the real tree boys pull in the Monster Bucks movies. Super long shots, Hang a deer target high up in a tree, put a target on a skateboard and push it, etc etc. Sounds pretty fun. Let us know the results

Jay