What are you looking for exactly? If you want a detailed system maybe GURPS would be your thing. It's a universal system, with a sourcebook for just about every setting you could imagine.
If you want something more cinematic, you can't go wrong with Unisystem Lite, as used in the Buffy game. Not exactly 12th century, but it would be rather simple to convert. Just get rid of the computer skill, maybe rename a couple of the others. Create some qualities (sort of like feats, they help define what a character is) to reflect what you want the PCs to be like, and you're good to go.