This is what happens when I read Terminal Space, Encounter Critical, and Bandits & Basilisks in the same weekend.
1. The "classic six" attributes, 3d6 straight down. No bonuses until 14, no penalties until 7. Ability lowering/raising per B/X D&D OR the ability to set one single score at 14 per SWN.
Str: affects hit and damage, "feat of strength"
Int. affects languages known and chance to learn spells.
Wis. affects saving throws vs. magic/psi
Dex. affects missile to-hit and armor class
Con. affects hit points and saving throws vs. poison
Cha. affects retainers and reaction rolls
2. Hit Points are d6 for everybody
Combat: Roll this at the beginning of a battle to select a bonus for the duration of that encounter. Starts at a % equal to your Str x 2.
Thievery: Roll this to do classic thiefly stuff. Starts at a % equal to Dex x 2
Sorcery: Roll this to learn spells, make potions, identify items, etc. Starts out at a percentage equal to your Int x 1.
You also get 15 percentage points to distribute among your skills as you see fit.
4. Alignment- Law, Neutral, or Chaos.
5. Equipment- Everyone gets 3d6x10 gp.
You must have Thieves' Tools to open locks and disarm traps.
Armor heavier than leather will give a penalty to climbing, sneaking, and other applications of Thievery at the GM's discretion.
Armor has no effect on Sorcery, as spells are never cast directly by mortals.
6. Magic- Characters who roll a successful check against Sorcery begin the game with one randomly determined spell.
7. Combat and Saving Throws: everyone uses the same tables as the B/X fighter.
Optional rule: You can switch the numbers around.
8. Experience- Use the fighter table from b/x. Each level, characters gain 1d6 hp, modified by Con. Characters also gain 10 percentage points to distribute, as they see fit, among their skills. Skills cannot be raised above 95%.
Optional Rules for non-human races:
Elf-To be an elf, a character must have Int and Dex of 13 or higher. All elves must be Chaotic in alignment.
Benefits- start with Sorcery= Int x2, always start with one spell and may roll for a second, double chance to detect noise or hidden doors. Elves are immortal as long as they return to their homeland every 1d4 centuries.
Drawbacks- Elves take double damage from iron weapons and can be warded away by magic such as Protection from Evil. The holy symbol of a Lawful religion will drive an elf back if he cannot save vs. magic, so long as it is presented by someone of non-Chaotic alignment.
Dwarf-To be a dwarf, a character must have Con of 14 or higher. All dwarves must be Lawfully aligned.
Benefits: Dwarves have +2 starting hit points and gain +2 extra hit points every level. When searching for/disarming traps or opening locks, dwarves have a +20% bonus to Thievery. Dwarves are immune to poison unless it is magical or extraplanar in origin.
Drawbacks: Dwarves have -1 to all attack rolls and saving throws made in daylight. A dwarf who finds a valuable gemstone (100 gp or more) must save vs. magic or consume the gemstone. He must roll for each gemstone, but once he consumes one he is sated for 1d6 months. A dwarf must eat at least one gemstone per level before he can advance to the next level.
Halfling- To be a halfling, a character must have a Strength of 13 or less and a Constitution of 9 or higher. Halflings must be Neutral in alignment.
Benefits: Halflings gain a +1 to hit with any thrown or ranged weapon. Halflings have a bonus of -2 AC against creatures larger than man-sized and -4 for truly giant opponents. Halflings double their Thievery score when trying to hide or be sneaky.
Drawbacks: Halflings must buy custom armor that costs 150% normal price to make. Halflings consume twice as many rations as other races. Halflings cannot use any melee weapon bigger than a short sword.