This is pretty much a new fighter from the ground up.
It's based most explicitly on the Lamentations of the Flame Princess: Weird Fantasy RPG fighter because that ruleset is free to download and pretty simple and just like most D&Ds, but this fighter here should be roughly compatible with all Old School games. Roughly compatible like: In the way Greg Ginn's guitar was roughly compatible with Rollins' vocals. Like...just off enough to be interesting.
-differentiates PCs mechanically a little more
-suggests a slightly more D&Dish, pile-of-goblin-skulls and less Cthulhu-esque-monster-of-the-week background than LOTFP, and
-makes levelling up a little more fun than it usually is.
Theoretically, you could also switch to this system in the middle of any D&D game at any time instead of taking whatever the usual level-up package in your game is, though you need to keep track of your own attack bonus and your own saves.
When you level up as a fighter in LOTFP 3 things happen: more hit points, attack bonus goes up, saves might get better. So in this...
WARRIOR (Fighter Variant)
...you start with your normal 0 level hit points and saves. Write those down.
At first level, and each time you level up, you get your hit points as usual, but instead of the attack bonus and saves improving on a schedule, you roll twice on this table. Do what it says--there are also indicators of what to do if you re-roll that same result over again in places where that's hard to figure out...
1-30 +1 to hit. Trust me, you'll be glad you have it.
31-50 +1 to all your saves Aren't you mr special goose? Or ms special goose
51-55 In battle there is no law, but you're kinda in charge. Once per fight you can give any other PC an extra non-attack (that is: not a traditional "roll to hit, roll for damage" type weapon attack), non-spellcasting action. Re-rolling this lets you do it one more time per fight.
56-57 When you hit things they tend to stay hit: +1 damage. If you roll this again it jumps to +3, then +5, +7 etc
58-59 You have learned where not to stand. +2 to jumping out of the way (reflex save, breath weapon save whatever it's called in your system). +1 thereafter if you re-roll this.
60-61 You smoke less and have been getting some exercise. +2 vs toxins, poisons and whatever other saves might be considered derivable from your general good health in the system you're using.
62-63 You've gotten real good at shoving. On a melee hit you can do your usual damage plus knock a human-sized opponent back ten feet. If you try it twice on the same opponent they get a save or str check or something against you. If you roll this result again you get 2 free shoves before the saves kick in. After that, re-roll.
64-65 You're good at getting people out of your way. On a melee hit you can do your usual damage plus knock a human-sized opponent prone. If you try it twice on the same opponent they get a save or str check or something against you. If you roll this result again on this table, you get 2 free knockdowns before the saves kick in, then 4, etc. After that, re-roll.
66-67 You're good at aiming for the fingers. On a hit you can do your ordinary damage plus disarm an opponent if they fail a simple str check. If you reroll this result they get a penalty to their check, +1, then +2 etc.
68-69 You're grabby as fuck. On a melee hit on a human-sized or smaller opponent you can do your ordinary damage plus your opponent is grabbed if they fail a strength check. Note grabbing is not always what it's cracked up to be since now you're vulnerable to attack from elsewhere, but enjoy it while it lasts. If you reroll this result they get a penalty to their check, +1, then +2 etc.
70-71 You've been getting out and meeting new people. You are now +2 to hit from horseback or +2 to hit in unarmed combat or +2 to hit with a bow or crossbow. Your choice. If you eventually roll all of those and keep re-rolling this result, you start getting +2s to weird fighting situations you can make up, like fighting blind or on fire or whatever GM approval blah blah blah
72-73 Finally! A second attack per round. You divide your attack bonus however you like between opponents/strikes. You get an extra attack per round every time you re-roll this result.
74-75 Christ you're big. +2 to checks to intimidate people. +2 when your re-roll this thereafter, you're getting like Wolverine scary.
76-77 You shall be splintered! Basically you can use the Shields Shall Be Splintered rule on a limb of your choice: A single hit that normally would have killed you just maimed you instead. You lose an arm below the elbow or leg below the knee, your choice. If you re-roll this you can "bank" another one or, if you've already lost a limb, the next time you get magically healed it comes back.
78 AHA!!! You've heard a rumor in a tavern--that thing you wanted? The riding panther? The Axe of Ninety Nymphs? That king totally willing to lend you his army? The parasitic extra limb that grants you immortality? That romantic subplot? It's there. 4 sessions worth of adventure away or less. Tell your GM, who then must place it.
You must have a fair shot at it--like any other treasure, but there's no guarantee you will get it. If you don't get it by the fourth session you can keep trying or let it go and roll again on this table. However if you choose to roll again and then you do get the thing somehow anyway, you lose whatever gimmick you rolled. GM think up some clever reason why.
79 Your smashingness inspires awe in lesser beings. You have an exceptionally (though not supernaturally) intelligent and loyal henchman, hound or horse (your choice). This individual cannot be slain, kidnapped or otherwise traduced "offscreen" by the GM, so if he or she's in trouble and your PC is not around you get to play it out. Of you re-roll this and your previous one is not dead, you get to add another hit die to your pal.
80-81 You're totally a skullsplitter. Your crit range extends by one. Now you double damage on a 19 or 20. Keep rolling this and it keeps extending.
82-83 You get those sunken eyes like Bronn in Game of Thrones. Immune to fear. If you re-roll this, your companions gain a +2 vs fear if they can see you, then +4 etc
84-86 Hold fools! I hear something.... Which of the following environments has your PC spent the most time fighting in: city, dungeon, wilderness, desert, or sea? Whichever it is, you can now anticipate wandering monsters a round ahead of time in that environment and are immune to nonmagic surprise there. If you re-roll this again you can pick a second environment or get an extra round of anticipation.
87-88 You have learned to aim jusssst above the eyes. When fighting an opponent with adjacent eyes you can do your normal damage plus partially blind it by getting blood in its eyes. It'll take the opponent an action to wipe the blood away and this trick only works once on any given opponent. If you re-roll this it takes two actions to wipe away, if you re-roll it again you can totally de-eye an opponent on a successful hit, if you re-roll it a fourth time then just re-roll until you get a different result.
89-90 You've been like hunting and stuff with your Ranger friends. You can now knock prone or shove anything that is animal intelligence up to the size of a bear in addition to also doing usual damage on a successful melee hit. Subsequently re-rolling this result gives you a +2 to damage vs animal-intelligence foes.
91-92 You have learned the Impetuous Immortal Leaping Strike. You leap six feet in the air and for a mere -2 to hit you can do double damage if you connect. You can't pull it twice on the same foe (even if you miss) and it's kinda exhausting and puts you in a bad position, defensively--you cannot attack in the round afterwards. If you re-roll this, the damage goes up by 2 points each time.
93 Hey whoa, been going to the gym, huh? +1str up to racial max. Numbers in excess go to con or dex.
94 Hey whoa, been doing like laps in pools of the tears of the families of your fallen foes? +1 con up to racial max. Numbers in excess go to str or dex.
95 You have an annoying drinking buddy who thinks throwing like wadded up paper at you is fun. +1 dex up to racial max. Numbers in excess go to str or con.
96-97 You have become unbelievably metal. You do triple damage on a crit. Re-roll this: you do quadruple, etc.
98-99 You're like a decapitator. If you roll a natural 20 against something with a head in melee and its level/HD is equal to or less than yours, it does not have a head anymore. Re-rolling this means you can do it against things your level or one higher, then 2 higher, etc.
00 Ab..ra...kaaaa..what? Holy hell, someone managed to teach you a spell. The formula is bouncing around in your brain dying to be unleashed. It's any spell you want, up to 8th level, and it will work as if cast by a 15th level Wizard. It will work once, period. Ever. You have to be able to speak in order for it to work but no other restrictions apply.
The Warrior must not become dazzled by the embarrassment of combatly options. You get 10 seconds to pick what you're doing once it's your turn, got it?
Warriors count foes slain (Michael Moscrip's idea, but spontaneously invented by fighter players everywhere since D&D began)--race and number.
For each combatant of a species (human, goblin, dragon, etc.) slain in-game (Warrior delivers the killing blow) the Warrior makes a notch. Once per encounter with that species (any time during the encounter), the Warrior's player may assess the creature. You assess by rolling percentile dice--
-if the first d10 is under the number slain, the AC, current hit points, and attack bonus of the creature are known,
-if the 2 d10s, taken as a 2-digit number, are lower than the total slain, the Warrior knows what the creature will do in the next round of combat (action and target, if any).
Swarms don't count, max is 90, slain after that just goes to bragging rights at your FLGS.
GMs are free to determine what constitutes a "species", fighters are free to bore everyone by killing endless orcs in their little orc sentry pits for no reason just to notch up, and the other players are free to have a little talk with them if they abuse these rights and perhaps should view them doing so as a nice little red flag.
Feel free to kick the tires on this. I am amenable to suggestions.
I am fond of the "big d100 table to level up" idea but then I would be, right?