Unknown Armies by Atlas Games
Your max HP is (generally) equal to your Body attribute (for a Street-level campaign on a character with all attributes equal, that would be 55 at character creation). Hand-to-hand weapons deal 2d10+X damage, where X is 0, 3, 6, or 9 depending on the characteristics of the weapon in question: 'piercing', 'large', and 'heavy' each add +3 to the weapon's damage. Ranged weapons deal d100 damage, with a maximum damage based on the ammunition used. (There are some types of ammo listed in the book with a maximum higher than 100, which is achievable with critical hits.) A character obsessed with their hand-to-hand attack skill could potentially deal ranged weapon damage using a H2H attack on a crit. Piercing weapons (knives, etc. – things which pierce the skin without requiring tremendous force) will inflict 1 damage on a miss.
One or two solid hits can easily bring someone into a serious danger zone. Further, in UA the GM is encouraged to keep track of the players' HP, and only describe the injuries rather than giving the actual number. While someone at full health could certainly try to keep track of their injuries themselves, injuries do not heal instantly (even a professional doctor with a well-equipped operating theater cannot fully heal an injury; characters still require convalescence if they wish to return to full health), and none of the published magical effects that I can recall will heal a target. In fact, one of the schools of magic requires the Adept to injure himself in order to build charges for spells, sometimes even reducing the character's maximum HP. That said, the setting provides plenty of room for custom Adept schools, if you happened to desire to create one about healing.
At approximately 2/3 health, a character suffers a -10 shift to attribute rolls. At 1/3, he or she suffers a -20 shift. (Shifts applied to rolls are in multiples of 10, ranging from -30 to +30, and all sources of shifts will stack.) At 5 HP, a character falls unconscious, and at 0 HP, they are dead, full stop. Considering the weakest possible attack in the game deals 2d10 damage, a margin of 5 HP is not very big.
With three exceptions I am aware of, all events in UA are resolved with a single die roll. For example, let's say Gary has a Struggle of 37, and tries to punch Steve. Gary rolls his d% with a result of 12 – success! The punch is not piercing, large, or heavy, so the damage is 2d10... which Gary already rolled. Steve takes 3 damage (12 = 1 + 2). Attack complete. Steve escalates by swinging a knife, rolling 02 under his meager Struggle of 18, dealing 15 damage (02 = 10 + 2, with an extra +3 for using a piercing weapon).
An exception fairly common in combat is dodging. If the target of an attack is using his action to dodge, the attacker rolls as normal. The defender then rolls his or her Dodge skill; if the defender succeeds on the roll and the Dodge roll was equal to or higher than the attacker's attack roll, the attack misses. If the defender fails but the attacker's roll is under the defender's Dodge, the attack deals half damage (round up).
If an Adept takes on negative shifts to cast a minor blast, he or she can use that many extra dice on the attack roll, picking any two to use for the attack roll result; still one roll, just using extra dice. If an Adept takes one or two extra turns to cast a significant blast, he or she can do the same thing.
The other exception applies only to characters whose obsession skill is the skill they're using to make a H2H attack with. If they roll successful doubles (11, 22, etc. under their attack skill), they get a "cherry". One of the possible cherries is adding 1d10 to the attack's damage, and another is rerolling the damage entirely.
It is possible for the PCs or NPCs to drag out a fight, of course. For example, a character could hide behind a piece of obstructing terrain or continuously use their action to dodge, waiting for their opponents to exhaust their ammunition. (Getting hit by a ranged weapon can hurt, after all!) If the attacker has a lot of ammo to run through, the defender might be waiting a while.
The designed setting for UA takes place in the modern world, rather than some high fantasy place like Middle Earth or Faerûn. The schools of magic include things more commonly seen in fantasy settings such as Cliomancy (history magic), Entropomancy (chaos magic), and Mechanomancy (clockwork/steampunk), but also include things like Plutomancy (money magic), Urbanomancy (city magic), and Pornomancy (exactly what it sounds like). The central conceit of the supernatural in UA is that if someone can be sufficiently obsessed with it, it can be done. As I recall, one of the supplemental books talks about a character who is obsessed with her collection of china dolls and, because of her obsession, the dolls come alive at night and protect her when she's not aware of it.
Most campaigns will ultimately take place in the "occult underground", that little bit of strangeness that permeates the world. Personally, I find the combination of realistic and fantastical elements fascinating. However, you're certainly not required to run a campaign in the Real World™. I have recently been running a game which is a spinoff from UA, using the vast majority of its rules, which takes place in the setting of My Little Pony: Friendship is Magic. The sky is the limit – literally so, in the case of my pegasus PCs.
Avoiding a Fight
I want the players to fight if they feel it is necessary, not because it is the easiest way of dealing with a problem.
This sentiment is aligned with some of the design process of UA. At the beginning of the combat chapter of the UA core book, the authors have this to share:
Six Ways to Stop a Fight
So before you make a grab for that knife, you should maybe think about a few things. This moment is frozen in time. You can still make a better choice.
Surrender. Is your pride really worth a human life? Drop your weapon, put up your hands, and tell them you're ready to cut a deal.You walk, and in exchange you give them something they need. Sidestep the current agenda. Offer them something unrelated to your dispute, and negotiate to find a solution.
Disarm. Knife on the table? Throw it out the window. Opponent with a gun? dodge until he's out of bullets. Deescelate the confrontation to fists, if possible. you can settle your differences with some brawling and still walk away, plus neither one of you has to face a murder charge or criminal investigation.
Rechannel. So you have a conflict. Settle it a smarter way. Arm wrestle, play cards, have a scavenger hunt, a drinking contest, anything that lets you establish a winner and a loser. Smart gamblers bet nothing they aren't willing to lose. Why put your life on the line?
Pass the Buck. Is there somebody more powerful than either one of you who is going to be angry that you two are coming to blows? Pretend you're all in the mafia and you can't just kill each other without kicking your dispute upstairs first. Let that symbolic superior make a decision. You both gain clout for not spilling blood.
Call the Cops. If you've got a grievance against somebody, let the police do your dirty work. File charges. Get a restraining order. Sue him in civil court for wrongful harm. You can beat him down without throwing a punch.
Run Away. The hell with it. Who needs this kind of heat? Blow town, get a job someplace else, build a new power base. Is the world really too small for the both of you? It's a big planet out there.