Plastic containers (soda, milk, bleach, etc.) filled with water and red dye.
I once (okay, 3 times) filled a soda bottle with gasoline, set a lit propane torch next to it and shot the bottle with a 270 from about 50 yards. Very impressive. My only regret was I had nobody to share it with.
Now that I'm 25 years older, more mature and have friends with the same interests I'll have to do it again with video!