For the game idea I've been working on (see city design thread below for slightly more info), I have a basic task resolution mechanic using d10 that works thus:

Players roll Xd10, where X = the relevant stat value (rated from 3-5: 3 being minor competence, 4 being basic and 5 being somewhat more of an expert and the maximum basic level - for simplicity's sake).
The task has a Difficulty level (rated 5 for simple/default level, 7 for complex, and 9 for difficult).
When the player makes his roll he must adjust the result to compensate for the difficulty in the following manner: working in ascending order he removes as many dice as is necessary whose running total must at least equal the Difficulty, removing no more dice when that total is reached. If there are any dice remaining the player succeeds with 1 Success value/remaining dice. If no dice remain, the action is deemed to have failed, a failure value may be derived from the values on the dice so removed if necessary (ie, i haven't got that far yet).
For example; I roll 4d10 against Difficult 7, average diff, 1,5,6,8 are my results. I must then remove the 1,5 and the 6 to create a total that at least matches the Diff (1+5=6, so the extra 6 is needed making 12). The remaining 8 is safe and i succeed with 1 success!

Interesting.  Why go in ascending order?

xenopulse wrote:
Interesting.  Why go in ascending order?

On reflection this doesn't offer a large range of success levels (max of five dice means 1-4 success at best). So here is an alternative. Proceed exactly the same except you create two dice totals and then compare the difference between to check for success.
After removing dice for difficulty, create the difficulty total from those dice. Then create a success total from the remaining dice. Subtract the former from the latter and the attempt is succesful if the difference is at least 1. The number of successes is equal to the difference as well, for further precision (use this for attack damage, frinstance). However this could potentially create a very high upper limit on successes.

Adding multiple dice is relatively slow for someone not mathematically inclined.

Done any success rate charts?
(ie, chance of any success given Y dice and X difficulty, chance of 2 or more successes, chance of 3 or more successes, chance of 4 or more successes)

Does the curve express what you want?

Tried using different die sizes -- possibly you'll get a better curve with a different size of die.

A good system should be simple and intuitive. On that note, I've had a change of plan.

To attempt an action, players roll (1d10 + stat, rated from 1 to 5) - (2dD). Those dice are rolled at once and a quick calculation is made. dD means Difficulty dice; difficulty is determined by either d4 (easy), d6 or d8 (hard), with possibly also d10 (very hard). Since two dice are rolled, they need not be uniform, to include greater variety of difficulty.

Make the roll and count what's greater than 0 (anything lower defaults to 0) as the number of successes you get. The only criticism is that it can lead to some wildly fluctuating results. This needn't be an issue I suspect.

Furthermore, there are two types of action: normal and stressed.

Normal actions resolve as above, with uniform dice.

Stressed actions are those where there is greater pressure and more to gain. This is where Grit comes into play. Grit is a trait based on the character's highest Stat value and depletes during a given scene (where stressed tests are made usually, such as moments of combat). a character who loses their Grit must sit out the remainder of the scene as a KO'd character; afterwards they return at full Grit. These points also fuel special abilities and talents.

During stressed tests players can gain or lose Grit; their current Grit also limits all stat values when making tests - unless a point of Grit is spent. Failure on a stressed test is a further loss of Grit. (That's as far as this system goes for now).

Finally characters can incur States, these are physical, mental and emotional conditions such as poisons, stress or smoke inhalation - anything. Each state will of course have its own effects and many, such as poison, can multiply creating a second instance thereof. Characters, above and beyond suffering the individual consequences thereof, can keep going so long as their Grit at least equal the number of States they currently have. If it dips below they are treated as if KO'd. At this point their Grit defaults to 0 and States no longer multiply (most will disappear). They return, as above, next scene as normal.

This is a rough outline so far, thoughts? It's a pulpy 'cinematic' setting, hence the Grit mechanic.

Oh and thanks for the comments thus far.