Basic Trope: As long as you have one HP left, you're fine; once you lose it, you're dead.
Straight: Bob is perfectly fine as long as he has one hit point left. No matter what he gets hit with, as long as he's alive, his performance is unimpaired.
Bob routinely walks through warzones taking hits left and right; he knows he'll be fine as long as he has that one HP.
Or, exaggerated in a different way, Bob is a One-Hit-Point Wonder. He gets a papercut on his finger and instantly falls over dead.
Downplayed: A character will start limping as he takes damage. He still uses his hands normally on any health level.
The Game characters are spirit beings, and HP measures their spirit energy which is what keeps them in the world, when that energy is reduced to zero they can't exist anymore.
Or you're in an FPS game where you have a shield which acts as "your health" and when that's gone, another shot is death
Inverted: The effects of damage are tracked ruthlessly. Unless proper medical attention is giving Bob will bleed out from just getting shot once some place nonessential. Trying to move too fast when injured can cause wounds to reopen.
Bob has about 500 HP left, but since he took so much damage in a vital area, he dies anyway.
Bob doesn't show any signs of weakness, but once he gets down to about 10% of his current HP, he starts complaining (via audio or text boxes) about how low his Hit Points are.
...But it's only a temporary death from a special Non-Lethal K.O. rule, and he's back on his feet after a little rest.
Bob dies with 500HP left because his legs have been blown off... but once he's healed to back to positive HP in that area his legs are mysteriously fine and he's up and running again.
Other than complaining about how low his HP is, Bob shows no ill effects to being blasted around.
Parodied: Bob walks around with dozens of swords and arrows stuck into his body, because they didn't do enough damage to kill him.
Zig Zagged: Bob the warrior can fight at full capacity at one HP, but Alice the ninja runs more slowly at low health. However, Bob's idle animations at low health show him clutching his arm with strained breathing, while Alice's limping only carries over to her running animations and does not affect her climbing ability or kick attacks.
Bob can take a fair amount of damage before dying, but every injury is painful and weakens him.
During battle, Bob changes conditions based on how many health he has, from full to zero: Fantastic, Good, Meh, Tired, Exhausted, KO'd.
Player performance was planned to degrade with damage but it got vetoed out of fears that it'd make the game less marketable.
Lampshaded: Alice says, "Wow, Bob, those arrows look uncomfortable. It's a good thing you have one hit point left."
Invoked: Healthy soldiers keep getting incapacitated early in battle even though they have non-lethal wounds, so the army invents special Power Armor and Energy Shields that keep their soldiers up and running until they run out of Hit Points, helping them fight longer and stronger.
Exploited: Bob faces down his gun-wielding rival, because he knows how much damage that gun can do, and knows he has enough hit points to survive being shot.
Defied: The rival knows that one bullet won't kill Bob, so he loaded his gun with tranquilizer darts instead.
Conversed: "You do realize I have one hit point left, and thus I'm not dead, right?"
Cradan exploits this fact, slowly and painfully bring his victims down to one hp repeatably.
Because he's feeling perfectly healthy, Bob forgets he has one hit point left and rushes his opponent, who proceeds to kill him instantly.
Reconstructed: It's an accepted fact that people will function perfectly until death, because all soldiers have full-body forcefields that keep them totally safe until they run out of power, but the weapons are powerful enough to vapourise you instantly.