I hate it when I'm at work and I can write a bunch of notes on a scrap of paper, each of those notes forming the trigger for a great blog entry about game mechanisms...only to lose those scraps of paper when I sit down at the computer. It's happened quite a few times over the course of the past year.
...and it's happened again now.
Since a new idea has come to mind, I'll consider it as something worthy to write about.
Player characters are all outsiders. This is a part of the quintessential hero myth, if the hero was like everyone else, they wouldn't be interesting to tell stories about. If a group of player characters were doing the same stuff that everyone else is doing, then it probably wouldn't be worthy for us to dedicate our imaginative efforts toward them.
A lot of early games played of this specifically. You are an adventurer who travels from town to town, ridding the local dungeons of their unsavoury inhabitants, and trading unearthed treasures for tools that will continue to help you explore new towns and dungeons.
Why don't the townsfolk go and rid the dungeons of evil?
Because they are either too weak, too frightened, or prevented from doing so by the local authorities (and this is where the extent of politics came into old school gaming).
More recent games have often sought to bring the player characters in contact with the world around them, integrating them into societies or factions (as I've described in previous mechanisms), byut it's still a case that the only independant thought in a game world typically comes from the player characters. Everyone else is going abut their daily duties, following their masters, reacting to the actions of the player characters, or engaging in their own grand plans that have taken weeks/months/years to set into fruition.
The players characters come in to upset the status quo, and for this reason they are treated differently by the people of the game world. They may be feared, hated, or sought for their skill and abilities.
Of course this is a bit of an over-generalisation. Villains are also removed from the population, and they may be feared, hated or adored just as much as the player characters.
A few games have mechanisms that show how much the key characters are separated from the rest of the world. Consider the class levels in early D&D...most regular folks are considered level 0, maybe level 1 if they've got a bit of experience, possibly level 2 or 3 if they are a part of the local militia or have marked themselves as prominent from some reason. The key characters in the world can quickly ascend to levels 10 or higher, and at this point they are truly removed from the regular folks.
Later editions of the game have allowed regular townsfolk to ascend through "NPC" classes, but these classes provide far less benefits at each level, and a plyer character at level 10 (in anything) far surpasses the abilities of a townsfolk at level 10 (in any NPC class). Those who choose to think for themselves and push against the world around them are both rewarded and cursed.
Another system to look at in this way is the Storyteller games of White Wolf. Vampiric Generation describes how far a character can transcend mortal bounds, but it also bring new levels of danger with every step removed from humanity. Magical Arete shows a persons ability to percieve the true nature of the universe, but with that knowledge comes susceptibility to the forces of paradox.
Many games play on this notion in other ways.
A character might possess a reputation trait that grows as they perform specific deeds. Gradually notifying to the outside world that this is someone to be noticed/feared/adored.
Looking back on my game "The Eighth Sea", I incorporated this concept into character's coherency ratings. Those characters who sought to make changes to the timestream based on their inner desires found their place in the timstream strengthened and their distance from the regular masses enhanced. Unlike some games though, I decided that if a character chose to give up their swashbuckling ways and fall back into the ebb and flow of the continuum, their coherency would gradually drop them back to normal levels.
I can't think of too many other games that reflect this side of the heroes path on a deeper level...the journey back to the mundane world. Sure, an adventurer returning to town after a dungeon is bringing back their find, but can an epic level hero settle down to a family life after years of adventuring? In most games it seems unlikely...but maybe that's just the crowds I've been playing with.
Once a hero transcend the world, there often seems no turning back.