Darth Bane had a Twi'lek master for a while who was a 'Blademaster' at the Sith Academy on Korriban. This guy knew all the lightsaber fighting styles, and taught all the sith at the academy that dual wielding was inherently a flawed style, and shouldn't be used. In reality, he secretly practised it himself, presumably because it's actually very powerful.
IIRC Revan is depicted as having dual sabers in some places, but whether this is canon or not, I don't know.
Luke Skywalker employed the use of a secondary, shorter lightsaber called a 'shoto' for a while. 'Shoto' is a Japanese word for short swords, and samurai sometimes used shoto's just like Jedi are showed as using. The Jedi are, obviously, based on samurai to some extent.