Yeah, and to add to this, how the player character reacts to damage or blunt force. In most games you get a red directional indicator showing where the damage is coming from, but that's it. The player basically just shrugs off AK-47 fire and tanks through it, or hides behind a mailbox and eats a pringle and it all goes away.
Why not have the player realistically take damage, no healing whatsoever. Just a take no prisoners pure tactical experience, maybe even stealthy experience. If you get shot you either find a place to wrap of tourniquet or you bleed out and try to finish, or even suicide out as is common in games if the wound is bad enough. Imagine a sort of Binding of Isaac type fps survival game where the only goal is to fend off enemies and survive as long as possible. No healing, no health packs, no real story, just lootable Pringles and Spam (our sponsors) for inspiration, and a lot of practice and leaderboards and PvP for online play. That would be cool game.