Every time I hear someone talk about the Conan game I like what I hear, I REALLY want that game.
I've looked at several of the d20 variants, and it's really the best one created (to my tastes). I think the Conan rules outshine Pathfinder, but I guess the universe of Conan doesn't have as broad an appeal.
Purely talking about the game rules, though? It's a fantastic game.
It's also a pretty gritty version of the d20 system. 20 points of damage from a single blow is considered Massive Damage and sees the target making a save or dying from that single strike. Armor absorbs damage--it doesn't make you harder to hit. You can Parry or Dodge blows, each with pros and cons.
It's viable to play a character wearing only a loincloth--this character would be heavy on the Dodge. Armor isn't unrealistic and ridiculous. You don't see men wearing complete plate mail running around dungeons. What you see is leather jerkins, chain shirts, brigadine, and sometimes breatplates. You can combine some armor types, too, making for more effective armor, as with a breastplate and chain. A supplemental book brings in piece meal armor, so you can just wear a helmet, bracers, and and shinguards--and still get some armor benefit, if you want to.
Weapons are rated with a penetration value. For example, a cutlass does good damage, but it has low penetration. A war hammer's damage is lower, but it's penetration is quite high. That's why you see pirates using cutlasses--because they usually go against non-armored foes, while the war hammer is home on the large battlefield where it is used to punch through heavily armored enemies.
The Conan RPG is also the best class-based system I've ever seen from a d20 based game. The classes are more a type of culture rather than a type of job. If you want to be a thief, then steal things. You don't need to actually have the Thief class. A pirate that lands on an island and charms the natives can be a High Priest just as easily as the scholar that's learned in the ways of a particular god or a high CHR warrior who has fanatical followers.
Multiclassing is easy and allows you to create any type of character. For example, a scout may be a Soldier/Barbarian or a Barbarian/Borderer. A pirate captain may be a Noble/Pirate. A bounty hunter might be a Borderer/Thief. Skills and ability are more important in this game than your character's class. And there is no Priest or Cleric or Mage or Sorcerer class. If you want to be a mage, then learn sorcerery. Scholars are best suited to this, but by no means is that the only way to be considered a sorcerer.
In fact, the Priest of Mitra that knows several spells may know more about Sorcerery than the thief dabbler that only knows one spell but got caught and has been run out of town for his diabolical ways.
It's a fantastic game. The designers did a fantastic job of creating Howard's Hyborian Age using it.
The one bit I have not seen in a rule system in many years that would enhance this is the idea that some languages are more difficult to learn than others. I liked Warlock back in the 80s because of that.
You want to see a great system for handling languages, check out the WEG D6 Star Wars game. It does have different difficulties not only for learning, but also for speaking some languages. So, if you roll bad, your accent is thick and maybe nobody understands you. Yet, the rule system is clean and easy. It would be like making a d20 skill check, with the result showing how well you spoke.
In fact, it would be easy to port over to a d20 based game.