Given that he is my favorite Sith Lord, here is my Darth Bane one...
Darth Bane is known primarily as a master of Djem So, however he also has Soresu and Juyo underneath his belt as well as an understanding of the other four forms to the point where he knows how to capably defend against and counter them.
With Djem So, Bane takes full advantage of his extraordinary physical attributes. Standing at a towering two meter height with strength enough to rip through durasteel, Djem So takes full advantage of the power he can work up from his strength and leverage. Djem So's focus on blocking and immediate counter-response also ensured that Bane was able to bring his full offensive capabilities to bear against his opponents. He was known to use his brute force to not only directly wear his opponents down, but he was also known to redirect his opponents blades at an angle that exposed them to a fatal strike or physical attack. Bane also doesn't fall victim to one of the more common weaknesses of Djem So practitioners, which would be a lack of mobility. Bane has shown himself to be a quick and agile fighter despite his hulking size, which has saved his ass on numerous occasions.
Another Form that factored into Bane's fighting style was Juyo. Bane used Juyo's unpredictability as an excellent compliment to his overwhelming application of Djem So, attacking from unpredictable and creative angles to make his already physically dominating offense even harder to deal with. Bane was known to reap the full benefits of his dark emotions when applying Juyo while at the same time attaining mastery and control over his emotions, not allowing his emotions to lead to an error in tactical judgement. In fact Bane's application of Juyo also involved probing his enemies defenses as much as attacking them with a controlled fury.
Soresu didn't figure into his offense, however his usage of Soresu in conjunction with his Djem So was quite interesting. Despite Bane's focus on offense, his mastery of Soresu ensured that he wasn't helpless fighting on the defensive and in fact allowed him to turn the tide of the fight back into his favor so he could resume his offensive. His defense was strong and nearly impenetrable, and his knowledge of how to defend against the other forms certainly came into handy here. Whenever placed on the defensive Bane would repel his enemy's strikes while waiting for an opening to assert himself into, effectively rebuilding his offense, and given the relentless nature of his fighting style this reassertion isn't something he'd be likely to lose.
Though Bane wasn't confirmed as being familiar with any hand to hand martial arts, he was quite skilled at chaining physical attacks into his offense, taking full advantage of the openings he creates with his Djem So technique.
Another thing that plays into Bane's lightsaber mastery quite nicely is his lightsaber itself. The nature of his curved hilt provided him with even more unfamiliar angles to attack from, bolstering his application of Juyo, while the way it fits into his hand provided him more power with some of his blows, fitting into his application of Djem So. The nature of its unfamiliar angles almost took off the arm of an implied Makashi master, a style that prizes itself on precision, in a single blow.
Bane was also known to use the force to not only increase his physical capabilities and senses through conventional methods, but he also took advantage of a power called inertia, which allowed him to alter his inertia and momentum, which has numerous applications that bolster his style. This allows him to increase the force behind his blows increasing his effectiveness with Djem So, as well as allowing him to change the direction of his motions and attacks more freely, adding to the unpredictable nature of Juyo, and increasing the effectiveness with which he can chain in his physical attacks.
One final element in Bane's fighting style is his tactical ingenuity. Not only does he favor unpredictability in his moves and maneuvers, but also in his overall tactics. He was known to probe for openings in defensive fighters, as well as taking advantage of his environment to seize a tactical edge, and was known to change his tactics every time his opponents get used to his current tactical approach, disturbing the rhythm of their engagement and effectively seizing control of the fight itself. He was also known to be highly adaptable to such tactic changes himself, quickly adapting and continuing to press his advantage.
So ultimately, Bane is a very physically overwhelming fighter on the offensive, taking full advantage of the benefits provided to him by Djem So, his raw physical capabilities, and his emotions. He's also a very unpredictable fighter, utilizing an unorthodox weapon, ever changing unpredictable tactics, the chaotic unpredictable nature of Juyo, and his ability to shift his inertia for physical attacks, or sudden shifts in angle and direction of attack. Within this offense however he also maintained a high level of control. All of this works really well on the offensive as it is increasingly difficult to defend against such powerful blows while dealing with such levels of unpredictability at the same time. This is further compounded by the psychological impact of defending against such a style would be frightening, especially since Bane knows how to use psychological ploys in fights. Such an assault is also much more deadly when you consider the amount of control Bane has over it. With his offense as good as this, his defensive capabilities are optimally engineered to restore his offense in a way that plays of the counter-responsive nature of Djem So as well as the nature of his control of inertia.
So to recap the summary that ran a little long, Bane's fighting style plays perfectly off of his physical attributes, armament, and bodily control, as well as being completely dominating and unpredictable with a defense that serves to re-orchestrate said offense. For these reasons I judge Darth Bane's fighting style to be unique, resourceful, and effective.