Component Advancement

Component Advancement

Description: Instead of gaining entire levels at once, a character earns one component of their next level at once. For example, hit points, spell slots, re-roll pool increases, etc. are gained separately, creating a gradual power increase.

Find it in: Low Fantasy Gaming, Cypher System

Keywords: Rules-light

Genres: Any Genre

Advantage/Disadvantage as Dice

Advantage/Disadvantage as Dice

Description: Rather than rolling twice and taking the higher result, you roll an extra d6 and apply it as a bonus to your current roll. Likewise, disadvantage involves rolling 1d6 and subtracting it from the roll.

Find it in: Shadow of the Demon Lord, Rogue 2e

Keywords: Fast-paced, Rules-light

Genres: Any Genre

Special thanks to Scott Weber for pointing me to examples of TTRPGs that use this as a core mechanic. 

A Lover's Comfort

 A Lover's Comfort

Description: A character who spends time in companionship (not necessarily sex) in a safe place with a lover or spouse gains non-cumulative bonus of+1 to Constitution or a similar measure of health and vitality for one week.

Find it in: The Islands of Purple-Haunted Putrescence (NSFW)

Keywords: Light-Hearted, Pulpy, Romantic

Genres: Any Genre

Progressive Damage

Progressive Damage

Contributed By: McChuck

Description:  Characters have few hit points, which are easily recovered outside an encounter. When hit points are exhausted in an encounter, the character takes ability/attribute damage. This may involve a saving throw to avoid being incapacitated or killed. The effects may depend upon which attribute/ability failed the save or reached zero.

Find it in: Into the Odd

Keywords : Dangerous, Gritty, Old-School, Tactical, Tense

Genre: Any Genre

Simplified Wounds

Simplified Wounds 

Description: Hit points are abstracted either into the number of Wounds that the target can take (in OSR games this is equal to HD). Any hit doing 4 or more damage deals a wound.
Find it in: Dungeoncraft
Keywords: Rules-light, Heroic, Fast-Paced
Genres: Any

Player-Facing Defense

Player-Facing Defense

Description: Game masters do not roll for attack, instead PCs have a defense ability they roll when attacked to beat a set attack value from a monster. 
Find it in: Knave, Maze Rats, Four Against Darkness, the Black Hack
Keywords: Rules-light, Heroic, Tactical, Player-Facing
Genres: Any

Zones - Subjective

Zones - Subjective

Description: Movement, reach, attack ranges, and spell effects are measured in zones: close, near, and far. Each is a relative distance from the character currently acting. So, close is close enough for the character in question to touch or engage in melee after just a few steps. Near is within range for a short-range spell a reach weapon or a sling. Far is something distant enough to require a bow or spell to attack and is too far to walk to and act in the same round. In some games this is interchangeable with objective zones. 

Find it in: the Black Hack, ICRPG Core 2e, Tiny Cthulhu
Keywords: Rules-Light, Fast-paced
Genres: Any

Zones - Objective

Zones - Objective

Description: Distance is abstracted into either three zones: near, far, and close or into two zones: here and there. The center of an encounter with the most action is counts as close, being at range to use short-range weapons and reach weapons places you at near, while ranged weapons and Magic attacks only places you at far. Or, being close enough to use a melee weapon is here, and being far enough away to use a ranged weapon is there. Movement, magic effects, Etc are abstracted to to work with this system. In some games this is interchangeable with subjective zones. 

Find it in: the Black Hack, Tiny Dungeon 2e, ICRPG Core 2e, 5e Hardcore Mode
Keywords: Rules-Light, Fast-paced
Genres: Any

Randomized Levelling

Randomized Levelling

Description: When leveling, a character rolls randomly for mechanical advancement, to make individual characters more unique. 
Find it in: Lion and Dragon, Star Adventurer, Gamma World 
Keywords: Old-School 
Genres: any

Depletion Dice

Depletion Dice

Description: Instead of tracking individual items like money, rations, and ammunition, a die can be expressed as a die. Each time the resource is taxed, the die is rolled to test whether that resource has been reduced in quantity, which is represented bt replacing the die with a smaller one on a dice chain. After a d4 fails a roll to avoid depletion, the resource is lost. Offers a visual way to track resources. 

Find it in: the Black Hack, Tiny Dungeon 2e 
Keywords: Rules-Light, Fast-paced, Cinematic, Pulpy
Genres: Any

Effort Pools

Effort Pools

Description: Setting a hit point total for a challenge that requires time and multiple rolls can be expressed as a hit point total. Characters' actions can thus be expressed as damage toward the total, making a single consistent mechanic for all tasks. 
Find it in: ICRPG Core 2e, 
Keywords: Rules-Light, Fast-Paced
Genres: Any

Progress Clocks

Progress Clocks

Description: Any task that requires more than a single roll, or a hazard that players may accidentally manifest through their action, are expressed a multi-part counter with 4-8 segments depending on complexity. A character fills 1-3 based on a degree of success with tasks until the click is filled, at which point the task is complete or the hazard comes to pass. 
Find it in: Blades in the Dark 
Keywords: Fast-Paced
Genres: Any

Room Target Numbers

Room Target Numbers

Description: Set a single d20 target number for all tasks in a room or for an encounter, allowing for modifiers based on the difficulty of the task being rolled for ease of tracking and play. Often made visible to players. 
Find it in: ICRPG Core 2e, 
Keywords: Rules-Light, Fast-Paced
Genres: Any

Re-Roll Pools

Re-Roll Pools

Description: Player's have a refreshing pool of times they may re-roll checks, applicable only to specific abilities of the character (like proficiencies), or Luck Checks. Replaces skill system and saving throw specialization. 
Find it in: Low Fantasy Gaming
Keywords: Rules-light
Genres: any

Daily Re-Roll

Daily Re-Roll

Description: Players have a single per session ability to force the re-roll of a single die. 
Find it in: Common House Rule
Keywords: - 
Genres: Any

Luck Scores

Luck Scores

Description: Characters have a depleting pool of Luck that may or may not Regenerate over time or as a RP reward. When no other roll seems appropriate to determine outcome, Luck can be rolled to see if a PC catches a break. It may be spent for bonuses. May replace saving throws. 
Find it in: Low Fantasy Gaming, Dungeon Crawl Classics RPG, Troika! 
Keywords: Pulpy
Genres: Any

Intercepting

Intercepting

Description: A character may sacrifice their turn to run their movement speed and block another moving character from reaching their destination. 
Find it in: Low Fantasy Gaming
Keywords: Tactical, Swashbuckling, Heroic
Genres: Any

Encumbrance Slots

Encumbrance Slots

Description: Instead of measuring gear by weight, give PCs a limited number of slots, either fixed or stat-based, in which items can be carried. Small items might fit in a single slot. Armor and very large items in multiples. 
Find it in: Lamentations of the Flame Princess, Knave, Maze Rats, Mausritter 
Keywords: Rules-light, Cinematic,
Genres: Any