Spell Fatigue

Spell Fatigue

Description: When casting spells, a magician takes an amount of non-magical damage based on the level or intensity of the Spell. Excessive use of Magic can cause the spellcasters penalties or fainting. Characters may be allowed to save to resist some of the damage. It is often used in conjunction with Spell Rolls.

Find it in: Shadowrun

Keywords: Fast-paced, Tactical, Weird 

Genres: Dark Fantasy, Low Fantasy, Horror, Science Fiction, Superhero, 

Simplified Early Firearms

Simplified Early Firearms

Description: Match-, wheel-, or Flint-Lock weapons take too long to load to be reloaded in battle without a hireling to load it, thus they may be fired only once per battle unless the character also carries (potentially explosive) pre-prepared shot, wadding, and powder bundles (called "apostles.") 

Find it in: Lamentations of the Flame Princess

Keywords: Exploration, Fast-paced, Gritty, Pulpy, Rules-light, Swashbuckling 

Genres: Crime, Dark Fantasy, Pulp

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. 

Last Breath

Last Breath

Description: As a PC is dying, there is a chance, if they might not otherwise recover of bein approached by Death, a demon, or otherworldly entity in a vision, and offered a chance to return to the world of the living, but they must agree to a quest. If they fail to keep up their end of the bargain in a timely fashion, they will die and be unable to return to life again.

Find it in: Dungeon World

Keywords: Dark, Epic, Fantastical, Heroic, High Magic, Weird

Genres: Sword & Sorcery, Dark Fantasy, Eldritch Horror, Epic Fantasy, High Fantasy, Superhero

Steal the Spotlight

Steal the Spotlight

(a.k.a. "Hold my beer", Time to Shine) 

Description: Once per session, characters get to declare that they are grandstanding and showing off their ability. They gain a vastly increased dice pool or double advantage on this roll.

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

Keywords: Cinematic, Epic, Fast-paced, Heroic, Pulpy, Swashbuckling 

Genres: Epic Fantasy, High Fantasy, Martial Arts, Pulp, Science Fiction, Superhero, 

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

Timed Initiative

Timed Initiative

Description: Players have a limited time to declare their action. If they do not have one to declare, they default to a defensive action.  Often used in conjunction with Simultaneous initiative. 
Find it in:  Dungeoncraft, Dungeon World
Keywords: Dark, Gritty, Dangerous, Fast-Paced
Genres: Sword and Sorcery, Post-apocalyptic, Low Fantasy 

Simultaneous Initiative

Simultaneous Initiative

Description: Players declare their actions without establishing initiative; the GM resolves all events in a phase order as if they happened nearly simultaneously. Creates a situation where combat is realistically confusing. 
Find it in:  Dungeoncraft, Dungeon World
Keywords: Dark, Gritty, Dangerous, Fast-Paced
Genres: Sword and Sorcery, Post-apocalyptic, Low Fantasy 

Armor Points

Armor Points

Description: Used in games that use hot points, wound levels, or damage tracks, Armor adds additional damage to the total the character can take that cannot heal unless the armor is repaired. 
Find it in: Blades in the Dark, Tiny Dungeon 2e, Pacts and Blades 
Keywords: Fast-paced, Tactical, Cinematic
Genres: Crime, Military, Sword and Sorcery, Low Fantasy, Science Fiction

Engagement Rolls

Engagement Rolls

Description: Stands in for a planning session, this roll allows a battle, heist, or similar planning-intensive adventure. The roll establishes the danger level and task difficulty as the adventure begins in media res. 
Find it in: Blades in the Dark 
Keywords: Fast-Paced
Genres: Crime, Military, Cyberpunk

Flashbacks

Flashbacks

Description: This system allows PCs to expend resources and risk harm to have an action occur in the past that gives the PC an advantage or potential solution in the present. Allows the PCs to dive directly into action and get the benefits of an extended planning session. 
Find it in: Blades in the Dark 
Keywords: Fast-Paced
Genres: Crime, Military, Cyberpunk, Western

Depletion Dice (Light)

Depletion Dice (Light) 

Description: Using a modification of the depletion dice, combustible light sources can be given a variable duration. 
Find it in: The Delve 2e
Keywords: Rules-Light, Fast-paced, Dark, Tense
Genres: Sword & Sorcery, Western, Low Fantasy, Post-apocalyptic, Horror 

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