Form XIII?
Alright, was anyone else completely weirded out by Sidious' Saber style? It seemed like something unique to the Sith that the Jedi wouldn't have done.
In terms of acrobatics it seemed like Form IV (Yoda's style) but in terms of fight stance seemed like a bizarre, two-handed combination of Kendo and Eppe (more emphasis on stabbing/poking than on slashing).
This makes his style incredibly lethal in close range, especially against any of the forms involving lot's of slashing like Dooku's Form II. Mace was able to beat him because he kept his distance and disarmed him with a lot of broad heavy strokes (a signiature of form VII), and Yoda was able to keep him at bay simply because of his fast movements and acrobatics.