Two ways to go. If you want a SHTF/TEOTWAWKI rifle, the Trijicon ACOG with .308 reticle is the way to go.
For hunting/plinking, I would get one of the 1-4 0r 1.5-5 scopes from Leupold, Nikon, etc.
Of course, it you can afford it, a Swarovski, Nightforce, S&B.. .............
And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.