Today I present you with this beast:
It looks like your typical AR-15/M16, what's so special about it? What's special is that this is an AR-10, a battle rifle which was the basis for the AR-15 platform. That's right, I said battle rifle. This is not an "assault rifle". This beauty is so powerful, it literally isn't in the same class as an M16 or AK47. This is a battle rifle. This is the rifle you grab when you realize you're the only one left and you STILL need to win.
The major difference between this rifle and an AR-15 is the caliber. The AR-15 fires the 5.56 NATO cartridge, and the AR-10 fires the 7.62 x 51 (.308). To picture below shows the difference in the size of these rounds:
On the right you have a AA battery, the middle is the 5.56, and the left is the 7.62 x 51. You often hear complaints that the 5.56 is an underpowered round, but the AR-15 platform has proven to be reliable and accurate. The AR-10 solves both of these problems. It has the best features of an AR-15 with the stopping power of a small tank, while at the same time maintaining a high degree of accuracy.
To sum up: the AR-10 is a powerful, accurate beast of a gun. If you can't take down your target with one of these bad boys, you probably shouldn't be taking on tanks with a rifle. Need a rifle that can pop that zombie 400+ yards away? Grab this. Need to make sure your target goes down and stays down? Grab this. Just love cool rifles? Grab this. I'm in love.