In the mid 90's I had a home brew sci-fi game that I called "Pair O' Dice" that gave a bonus to skills on a FAILED skill check. That way you were always rewarded for trying something.
IIRC, on a failed skill check you earned the less of your %chance of success or failure * 1% to the skill.
if you had a 50% skill, on an unmodified failure, you get +0.5% to the skill. But if you had either a +25 or -25 modifier to the check (75% success or 25% success), a failure would only give +0.25%.
The purpose of that rule was to make it so that you didn't gain much from trying ludicrously easy or nearly impossible tasks and gained more for attempting tasks appropriate to your skill.
I can't really say it is my favorite, leveling by overcoming challenges like in d20 modern is a lot more balanced and flexible, but its something you guys probably have not seen before.