(Jumping off a post of mine to the S7S list, though I'm pretty sure I've seen some other systems that do something similar, like see this post.)
Menu Resolution is a resolution system that you could drop into most any RPG where you roll to succeed and have a margin of success (or number of successes or whatever). Basically, the idea is you break down the idea of "a successful action" into small chunks, and you price each one in terms of points. Characters get points based on their rolls, and can buy whatever they want off the menu, and then a final resolution is narrated based on what they bought or didn't buy.
There isn't anything more to it than this idea, so here are some examples. Here's one for jumping across a chasm:
|Don't fall in||1 pt|
|Get across||3 pts|
|Stay on your feet||3 pts|
|Not make a lot of noise||2 pts|
The PC rolls their jump check and gets 4 points. They can therefore decide to not fall in and get across, but to do so noisily and to not stay on their feet (so presumably they do a belly-flop). Or they might decide to abort the jump and buy not falling in and staying on their feet (maybe they stumble and skid to a stop right on the edge). If they earned more points from their roll, of course, they might be able to afford to get across and stay on their feet and do it silently.
Note that you use the exact same system for things that are traditionally opposed actions, like combat. In this system the opposition comes from what you each choose to purchase. Like thus:
|Stab in the arm||2 pts|
|Stab in the leg||2 pts|
|Stab in the chest||4 pts|
|Stab in the face||8 pts|
|Total parry||3 pts|
|Partial parry||1 pt|
So, say, your opponent buys stab in the arm, stab in the arm, stab in the face. You have 9 points, so you could buy three total parries. Or you could decide to take one of the hits and buy a stab in the leg instead of parrying. Or you could take all three of the hits and do a stab in the face. (The real system would have more complicated choices than this, I expect, like paying now to do a feint next turn, or somehow positioning yourself to make other moves cheaper.)
This would also be good for slightly unpredictable magic systems — you can afford to make a big fireball or a precisely-placed one, which do you pick? Or maybe you'd rather just pay to have the spell fizzle, if you can afford that.
I didn't mention this above but obviously the players can say "I want to grab the guard on the other side of the chasm and pull him in, how much is that?" and the GM can quote a price. In general actions should be formed in as fine-grained a way as possible — it would probably be better here to have separate items for "I grab the guard" and "and then I pull him in" — to allow the player to really decide which they want and which they don't. They might roll, only get a few points, and decide they'd really rather pull the guard into the chasm silently than get across safely themselves, so then you get a cool scene with them struggling on a ledge midway down the chasm.