Narrative Ranking System

This is the combat ranking system, developed from the original numerical ranking system, used in GRIT Begins.

Ranks

1. Extra: Irrelevant normal-person bystanders and such - NPCs without names and backstories, certainly not PCs.
2. Non-Combatant: These individuals are those who are relevant to the plot, but can't make a meaningful contribution to combat.
3. Sidekick: These individuals are "special" compared to normal people, but aren't intended to play a major role in combat; they can contribute, but they're more likely to be the type of characters who are dismissed or kidnapped by the BBEG than those fighting him/her. These are the sorts of characters who are often narratively sidetracked (such as by opposing Sidekicks, or secondary goals which will help the Heroes fight) to keep them from meeting a grisly end in major fights.
4. Combatant: Maybe the trickiest to define, these are characters who are more important and effective than Sidekicks, but don't demand the same kind of narrative attention as Heroes/Villains do. Combatants have the ability to contribute meaningfully to a battle, but aren't going to beat a Hero/Villain without clever planning or favourable circumstances. They can't simply be dismissed by the BBEG, but they aren't likely to be the keystone of victory for their side, either.
5. Hero/Villain: The majority of our "main" characters belong here. They're major players in combat, but not so much so that they can dictate the path of a large combat the way a BBEG can. These are the characters who usually win battles, simply because they're the focal point of the story (at least insofar as it relates to combat). In the case of bad guys, this group includes antagonists who are intended to be a good matchup for a solitary Hero, or to fight in a team against a group of Heroes.
6. Sensei: These are rare characters of exceptional power, often the mentors and/or teachers of Heroes or Villains. Although these characters are often a lot stronger than the main characters, the narrative generally conspires to prevent them from being fully effective in combat situations - things like specialised planning by the opponents, important side goals, a need for discretion, crippling neuroses, whatever - and force them to make way for the main characters.
7. BBEG: As in, Big Bad Evil Guy(tm). Unlike the average Villain, a BBEG is the sort who can mantain the upper hand and dictate the flow of combat even when she/he is pitted against multiple Heroes. Although they generally exist with the intent that they will be defeated by the Heroes, BBEGs are the type of central antagonists encountered at the ends of plot arcs, and are extremely dangerous opponents even for groups.

This ranking system is based on narrative causality - which is apparently what the previous system was supposed to do anyway. Fox, who wrote this version of the system, loved the idea that GRIT could run on something so simple - "and let's face it, any actual numbers we apply to combat are always going to be ignored if doing so makes for a better story :p". The important part of the system is that all players need to keep in mind that what's being noted here is not a level of power so much as a guideline for the role a character should play in a given combat, and how their players want them to be respected in such.

Example: Bleach

The folowing is taken from Fox's post introducing the narrative system:

I wanted to give examples, but the only series I currently know well enough to use is Bleach, so I hope that will be familiar to at least some of you ^^; Specifically, from the Soul Society arc. I know a few of you watch the series, so hopefully this won't be totally wasted. I apologise if this spoilers anybody, but if you haven't seen the series, this won't mean anything to you anyway, so you may as well ignore it ^_^;

• Non-Combatant: Hanatarou. Played a key role in the plot, but was completely disinvolved in combat.
• Sidekick: Orihime. Significant abilities over a normal person, and could contribute to some early combats, but had problems taking down even low-tier opponents in Soul Society.
• Combatant: Ganju, Chad. Both held their own easily against low-tier opponents, but struggled against important oppponents, and couldn't really put up a fight against captains.
• Hero/Villain: Ichigo (duh), Ishida, Renji. Major players who took part in big, important battles. While they had somewhat varying degrees of success against captain-level opponents, they all put up a serious fight. As the actual main character, Ichigo emerges ahead by virtue of having more narrative favour up his sleeve, but the others are still relatively close matches.
• Sensei: Urahara, Yoruichi, most captains. Urahara is classic Sensei, obviously being very powerful, but completely unable to participate in any combat in this arc. Likewise Yoruichi - and almost all of the Soul Society captains - were removed from the need to face the main character directly, sidetracked by different plot threads and by other "Sensei" level characters.
• BBEG: Uh… that character who turned out to be the one behind it all. You know the one. Virtually single-handedly controlled or manipulated almost all the other characters for some time, was only kept from killing half the cast by virtue of pretty much everybody showing up as opponents.

In any case, I think one of the important points about this system is that when it's seen in an anime or manga, the definitions aren't stable, but are relative to the main character(s). Byakuya easily qualifies for BBEG status when he first confronts Ichigo at the end of the first arc, but as a major solo encounter in the second arc, he's brought down to the Hero/Villain level. Personally I find this pretty appealing, since it means power levels in the game will always be anchored to the average abilities of Hero/Villain characters.