Grunt in a barrel

The Grunt in a Barrel is an easter egg included in the Anniversary Map Pack on the multiplayer map Penance. It causes a Grunt model inside a wooden barrel to occasionally be sent over the waterfall into the water below.

Details
At the waterfall a Grunt in a wooden barrel will spawn after a random period of time and fall over the waterfall. If it lands in the water it will sink and disappear, but one can create a structure on Forge to catch the Grunt.

The Grunt itself has no mask, no methane pack, and does not move or respond. It is in its default "T-pose" wearing untextured armor (causing it appear as solid black) and is standing inside a wooden barrel. The easter egg as a whole is a reference to adventurers who had ridden over Niagara Falls in a barrel, such as Annie Edson Taylor, or Bobby Leach.

Trivia
This easter egg was featured in Rooster Teeth's Top 10 Easter Eggs of 2011. This easter egg specifically made the list at #4.