There is certainly a difference between inventing and making popular. I can give a well known example of a fantasy character written before Salvatore was even born. Galdalf was a dual wielder with both sword and staff. He used both in The Hobbit as well as wielding both Glamdring and his wizard's staff against the Balrog in The Fellowship, and I am not talking about the movies but the actual novels. Who knows, maybe Salvatore was inspired by Tolkien, the father of modern fantasy?
Agreed about popularizing or inventing, but Gandalf is not a good example. He used a staff. He may have even used a sword. I've read that entire series and he never used both at the same time.
Drizzt brought that idea to our conciousness... Tolkien didnt.