.577 Tyrannosaur
.577 Tyrranosaur was originally developed by A-Square, a firearms and ammunition company (and SAAMI member) in South Dakota that specializes in BIG rifles for large and dangerous game. .577 "T-Rex" is one of the most powerful cartridges on the planet, and has been known to push a 750 grain (>1.7 oz., ~50 gm.) solid, milled copper bullet at over 2400 fps, for a muzzle energy approaching 11000 ft·lbf from a 26 inch barrel.

When fired from the Hannibal rifle, designed specifically for the .577 T-Rex by A-Square, it has the distinction of the most powerful recoil of any commercially available shoulder-fired weapon on the planet - about 250 lbs. of force on the shoulder. Even the larger caliber .700 Nitro Express with a 1,000 grain solid projectile delivers only about 200 lbs. of recoil from the same rifle. Chances are, when you're watching one of those "GUY GETS KNOCKED DOWN BY 50 CAL RECOIL!!!!! LOL" videos on YouTube, it's actually a .577 T-Rex.

Aside from absurd ballistics and recoil, the .577 T-Rex, fired from A-Square's Hannibal rifle, is capable of astonishing accuracy - 1.25 inch groups of 10 at 100 yards are common. For reference - that's a group size just a hair more than two bullet widths. Given that the intended targets have kill zones anywhere from 10-100 times that, even at suboptimal angles, and you're talking about an extremely capable weapon for its intended purposes.