S.A.V.A.G.E. Essentials

Survival And Victory After Global Extinction

From the introduction:

This is the Essentials version of S.A.V.A.G.E., meaning it has been stripped down to the core rules only. Artwork is minimal, layout is basic, and it does not include a campaign setting, bestiary, artifact listing, or pre-made adventure that you will find in the full version of the rules. What this does have is all you need to play the game, including a character sheet and the full guidelines for weapon creation.

It should be noted that this game is for experienced gamers only, as the rules are very detailed and are meant to add an element of realism, flexibility, and squad level tactics to the gaming experience.