I'm always thinking about new mechanics to bond my players to each other. Most games rely on simple "safety in numbers" mechanics - if your cleric dies, you can't be healed. But that leads to very shallow relationships. "Working" relationships. Sure, players can exceed that, but it's kind of erratic when you have to fight the system.
Those aren't really what I like to see, so I try to use mechanics to make different kinds of relationships. Here are some of them.
Someone Else Narrates for You. I originally saw this method in a game that duplicates that Japanese movie about a high school class being shipped off to a deserted island and forced to kill each other. The idea is that you have to specify a best friend and a rival. If you succeed at something, your best friend narrates what happens. If you fail at something, your rival narrates what happens.
When I first saw it, I was rather taken with the idea, but in playtests it didn't work so well. With five players, a certain person ended up on every single other player's sheet as either rival or friend. They spent a considerable amount of time narrating. Awkward. Also, the position of "rival" is an unenviable one, and if done correctly, makes the players hate each other.
While there's something cool about this mechanic, I don't think it can be used like this.
Unique Card Requirements. In a Jedi game I ran, the Force was represented by cards - each player had a "hand" representing their access to the Force in any given location. Players were allowed to trade cards. At the beginning, trading cards was only done to "supercharge" a given Jedi: "Alex needs to stop the droid army! Everyone, give him all your face cards!" (There was also a noble sacrifice mechanic for Jedi who used more Force than they were supposed to, or used Force in a particular way.)
However, as the game went on, each character began to get specific card combinations that they could use more efficiently. One person would get double points if all the cards they played were hearts. Another needed straits, another needed face cards, another was good with deuces...
A chunk of our table time was therefore dedicated to swapping Force cards. While it sounds like this would break immersion, it really didn't. Perhaps because it made sense for Jedi to spend quite a bit of time communing with each other, perhaps just because of the peculiarities of our player base. But what ended up happening is that they all started to rely on each other far more than usually happens - far more than in other Jedi games I've run.
All Fall Down. I've seen a mechanic like this in many games, although I've never used it myself. Basically, the players have a shared set of... something. As they do cool stuff, they have to reduce that resource. At some point - exactly when is unknown - the resource will fall, and the player will die.
An example is using a Jenga tower: every time you need to succeed, you need to remove a piece. If it falls, you die. Another example is a simple card deck: draw two cards, put one back on top of the deck. If you keep a joker, you die.
These mechanics are interesting and work very well, so long as you're doing a relatively short narrative arc - one or two sessions. There's something about the randomness inherent in the system that makes it unsuitable for longer arcs, which generally have a stronger emotional investment on the player's part.
Source Control. In this kind of system, in order to do something, a player must use another character somehow. Generally, this is some kind of karmic link or psychic power source or something. However, it drains the second character somewhat.
This kind of system generally produces very political gameplay, because resources are limited and negotiation is king. When it actually harms you to help someone, players generally start bartering rather than simply being friends.
However, if the mechanic doesn't rely on limited resources, it can produce very interesting, deep relationships. For example, in order to use magic, you need to draw on your relationship to another character by partaking of that relationship. IE, friends have to banter, rivals have to try to out do each other, masters have to be obeyed, etc. If each kind of relationship can also only provide specific kinds of fuels, you can have characters who are actively searching for rivals, or masters, or lovers, or whatever. It's still very political, but in a very... narrativistic way, rather than a statistical way.
Can you think of any other methods of shared resources which get players to work together? Have you ever run a game with anything like this?
Actually, I don't think I have any GMs who read this blog. It's mostly computer gamers. I should probably stop posting this RP stuff.