Mount your friends!

"Mount Your Friends is a physics based competitive climbing game where what you climb is each other. Players take turns climbing to the top of a tower of previous climbers (and a goat) working to become the new highest point before time runs out. If you run out of time before reaching the top, you're eliminated. It's simple to get into, but difficulty to master. Adept competitors can create massive towers by flinging themselves faster than simple climbing methods can attain. Of course, you may also end up just falling all the way down a tower if you miss!"
steam- http://store.steampowered.com/app/296470/

 

The graphics are... interesting.