My favorite meta-mechanic is the 'currency' bonus from Sorcerer. It's a dice pool system where a successful roll results in one or more victories (think Successes from a white wolf game and it's pretty much the same thing). Your victories from one roll can become bonus or penalty dice on any related roll.
So say you're playing a thief, and you're trying to lift a key from the pocket of an NPC clerk. You roll your test and just fail -- the NPC wins with one victory. So when you try to save your hide by distracting the clerk ("what in the world could that be?!"), he'll get one bonus die to not be fooled. But say you win that test with two victories: then you'll get two bonus dice on your attempt to beat it and lose him in the crowd.
You can port it over into nearly any system. It's easiest with dice pools like nWoD, but you can also do it with d20. A +2 bonus, with another +2 per 5 full points of your margin of success, seems balanced for D&D.
So say you're playing a thief, and you're trying to lift a key from the pocket of an NPC clerk. You roll your test and just fail -- the NPC wins with one victory. So when you try to save your hide by distracting the clerk ("what in the world could that be?!"), he'll get one bonus die to not be fooled. But say you win that test with two victories: then you'll get two bonus dice on your attempt to beat it and lose him in the crowd.
You can port it over into nearly any system. It's easiest with dice pools like nWoD, but you can also do it with d20. A +2 bonus, with another +2 per 5 full points of your margin of success, seems balanced for D&D.