I can think of a non-D20 one fairly readily.
Changeling: The Dreaming, by White Wolf.
When a friend first showed it to me, I thought it was very dry, a bit silly, and very quirky... not to mention exemplifying everything I DIDN'T like about White Wolf (Mind you, overall, I DO like White Wolf)... I mean, for gawds sake... it's magic system uses terms like "Actor" "Prop" and "Scene" to determine spell targets and so forth.
Well, I still think it's kinda quirky at times... And the whole Actor/Prop/Scene/Etc thing DOES still irk me a bit, but the product on a whole is very cool. Easily my third favorite whitewolf setting, if not the second*. It's one of the least grim settings White Wolf puts out (It has it's own grim parts... the constant balance you have to play with Banality and Bedlam, for example), but it's a lot... brighter... than most White Wolf. And it's a LOT of fun to either play OR GM, in my experience. You can really create some imaginative characters, and not be at all "out of character" in doing so.
*(Nothing comes close to Exalted, and Changeling comes in a VERY close third, next to Sorcerer... Not Mage: Sorcerer's Crusade, but Sorcerer... a suplement for Mage that all but stands on it's own, much like how Demon Hunter X stands on it's own, but it still technicly a Vampire: Kindred of the East product).