I shoot whatever trash I can find... Soda bottles and cans, beer cans... I've shot at gallon water jugs or detergent bottles, pumpkins, cantalopes, etc...
My favorite is taking 4-5 gallon jugs and putting them into a line, shoot into the first and usually the bullet will stop before the last one. Catching a nice hollowpoint bullet is pretty sweet to look at.
I think the best tripwas shooting at the cow, chicken, dog, and pig that was leftover from my nephews birthday party (October)... see the attached pics below:
(edit - The land we shoot on is posted as private property. We shoot on a downhill slope, so any bullet that passes our target is aimed towards the ground... And, we always do a check for people prior to shooting too... And, we're at a cabin that has no neighbors for at least a mile in each direction)... Just incase anyone flames for not having a backstop.