Here is a narrative very-rules-lite mechanism I've been toying with, very much like my "Pulp in the Cup" game, only with cards instead of dice.
SOCIAL CONTRACT: Players design characters and navigate them through a world managed by a Game Master (GM) who conceives of the world and functions as the eyes and ears of the world for the characters. The Game Master also fairly applies the rules of the game, designs the story that the player's characters experience, and tries to assure that the players have a high quality time.
SETTING: The game setting is any setting familiar to all the player's and the Game Master, whether from some popular franchise or designed by the GM.
CHARACTERS: Character design is by straight description. Given the setting and other restrictions set by the GM, the player conceives of a character that fits the setting in a logical and coherent way. The working assumption is that the level of ability of the character is generally adequate to the level of challenge provided by the adventure according to the world of the narrative and is not either over qualified or under qualified for it. A good way to invite the player to design his character is ask him to be able to answer questions such as "How did your character come to be qualified to face this adventure?" and "What motivation led your character to accept this adventure?". The "Character Sheet" is simply the character notes made by the player about his character.
THE DECK: From a standard deck of playing cards, construct a deck of fourteen cards like so:
One black ace
One black deuce
One black four
Both red aces
Both red deuces
Seven picture cards (any mix of suits)
The value of the cards are as follows:
All aces are 1 point.
All deuces are 2 points.
The four is 4 points.
All picture cards are 0 points.
The sum of the points of the black cards represents the quality of the action taken by the character (higher is better). The sum of the points of the red cards represents the quality of the residence to the action by the circumstances (higher is greater). If there are no cards for one or the other color, the sum for that color is 0.
THE RULES:
Standard actions: In the course of playing, if a player 's character finds himself in a situation where he needs to make an action, the situation should be resolved logically from the character's description and the description of the setting. As much as possible, logic and plausibility should decide if a player's action was successful. If there is a chance of failure, resolve the action by the following means:
Have the character's player (which is the GM in the case of non-player characters) shuffle and cut the deck, then deal seven cards off the top. Fan and examine the hand. If the sum of the black cards is larger than the sum of the red cards, the action was a success. The difference between the black and red sums indicates the degree of success of failure. As with 'Pulp in the Cup', the GM describes what happened is such a way as to justify the figures in the result.
If its decided that the cards are necessary to resolve an action, the results should as often as possible be unmodified. But the logic of the description may require that the character be considered especially advantaged or disadvantaged in performing an action. In such a case, the GM may make a subjective judgment of the net difficulty and assign a value from +4 (nearly impossible) to -4 (nearly fool-proof) before the cards are dealt and add the modifier to the black card result before comparing. This modifier can be discussed with the players for cogency but the GM's ruling is final.
Critical successes and fumbles: If the degree of success on the pre-modified deal is +5 or more, the actions was a "critical success" and may have benefits beyond the goal of the action. Similarly, if the degree of failure of an pre-modified deal was -5 or less, the action was a fumble and has other detrimental consequences for the character making the action. The GM determines what these benefits or consequences are.
Resistance deals: If the character is not the acting agent but the recipient of the action (being enchanted, being poisoned, being diseased, etc.) the character's player shuffles, cuts and deals the cards as with a standard action, except the black cards represent the success of the action performed on the character and the red sum represents the resistance to it by the character. These deals may also be modified if deemed appropriate and they may also be critical successes and fumbles.
Combat: Combat between characters, if the story calls for it, proceeds in the following steps:
1. Determine surprise
2. Determine initiative order
3. Resolve combat actions according to initiative order
4. Repeat steps 2 and 3 until combat is over
If characters do not simply enter the arena of combat on an equal footing, it may be that one opponent may surprise the other. This is settled by a standard action deal using the relevant attribute of the character who is trying to gain surprise against the resistance of the character being surprised (such stealthy movement versus keen sightedness). Again, the description of the characters is decisive. If surprise is successful, the character gaining surprise gets a free attack without retaliation before combat starts. Once surprise has been determined and resolved, proceed to 2.
Initiative Order: Initiative is determined by shuffling the deck and dealing two cards to each combatant. The total number of points (red and black) is taken and whoever has the highest sum is first, then the next and the next. If there are ties, each tied character receives another card to determine the order between them. Keep doing this until all tied characters are resolved. If you run out of cards, go by birth dates or first names. The GM may decide to redo the initiative order after each cycle of combat or keep the initiative order until combat is finished, only adjusting it if combat effects it. It is possible that a character may have an advantage in initiative. In this case, the GM subjectively assigns a number (from 1 - 4) and adds that to each deal (initial deal plus tie breakers).
Combat Action: When a player's turn (or the GM's when the attacker is a non-player character) in the initiative order comes up, the player describes the attack and makes a standard action deal. This may be modified as any other standard action. The effects of a successful attack (a hit) are proportionate to the degree of success indicated by the deal and are determined by the GM (based on skill of the attacker, type of weapon used, etc.). A critical success indicates extended effects (crippling, losing an arm, insanity). A fumble indicates damage to the attackers self (his body or weapon). One of the effects of an attack could be to advance or lose one's place in the initiative order. The GM is encouraged to think creatively about combat and consider how to resolve running away, attacks prepared for in advance of combat, attacks of opportunity, and so on.
End of Combat: Combat continues until one character is incapable of fighting or tries to escape, possibly creating an opportunity for a free attack as in the case of surprise. Not all combat necessarily ends in death. It may end when a character is unconscious or incapacitated. If the character does not need emergency help he should get better over time with sufficient attention. Otherwise, the player will die without special assistance. Again, this should be resolved in the GM's story.
Powers: It is important to maintain the rule that the level of the characters ability is appropriate to the level of the adventure. Introducing powers must be done carefully. Some powers can be treated as skilled standard actions (psychic powers), some as resistance deals (spells) that cost the power user in some way (money, sanity, mana, physical damage), or some may just be part of the definition of the world and always resolve in some predetermined way (super powers). It's up to the GM to decide what world best for his story.
THE END OF THE GAME: This is also a pick-up game and there is no provision for experience points. However, it is possible to have the players keep their character sheets and replay there characters in another adventure. The GM is free to augment the character description to correspond with the in-game experience of the character but the real indication of this is that the character is promoted in rank and is qualified to go on even more challenging adventures than before.
When the game is over, pick up your deck and put it in your shirt pocket.