QEV gun, 30 bar, 16mm marble in the barrel.
Shot into some particle boards bolted together, marble bounced back with quite some velocity and bounced off my cheek.
I GAVE MYSELF A HEADSHOT!

It didn't do real damage, but left a red mark, and a raised heartbeat...
If it would've hit straight on instead of bouncing off, it would've hit harder then a paintball in the face (without a mask). A few inches from my eye...