From Chainmail to D&D Next
Barbarians of Lemuria
BoL is a quick playing Sword and Sorcery game, It’s a rules light game with an old school feel. The system is simple and quick, requiring just 2d6 with a form of advantage and disadvantage. Character creation is a quick point buy system based on carriers, and creates pulp action warrior and sorcery characters with ease, that start out very capable. Combat flows well without being too tactical. Armor soaks damage instead of making you harder to hit. Magic is freeform.
If more in-depth combat is desire back port the combat maneuvers form Honor+Intrigue, a variation of the rules to handle swashbuckling. Adding these dueling rules may enhance the individual nature of sword and sorcery, but it will slow combat down some.
Play when you have characters that want a pulp Sword and Sorcery game that plays quickly with a tradition feel. For players coming from D&D this would be at the top of my list to introduce them to a rules light game. This is not a resource focused game so its not going to do a dungeon crawl, but if you want to play Grey Mouser this system is great.