Here's my personal favorite: It's called "Holy Sh--- are you OK??!!"
Here's how to play...Dress yer friend up in a hockey uniform with all the pads. Have them to stand behind yer horse. You'll have a lariat rope around yer horse's flanks, just dangling loose. When yer friend is ready, yank the rope tight and watch yer friend get double-barreled!!! Don't worry about liability issues, you'd be surprised at the beating a human body can withstand