I have to figure out action moves and the camera movements and angles for them while animating Japanese 3D arcade game characters at work, so I have a rough idea on what probably works for fight scenes. It helped that I read a lot of Vagabond by Takehiko Inoue -- which I highly recommend. They say it reads like an Akira Kurosawa film on paper and for good reason.
These are some tips and tricks that might work:
1) Slanted borders for panels instead of them being perpendicular.
2) Tilt the camera diagonally instead of upright.
3) Avoid having panels with similar angles, zooms and character poses situated side by side. The more variety the better.
4) A full-bodied side view of the two battling characters to show a defining moment. Suitable for sword fights and duels.
These are examples shown in Vagabond:
5) The 180 degree rule may be broken because of all the action going on and that's forgivable. But it still applies even after they switch places. The characters don't have to be in the centre:
Sword of the Stranger has one of the most beautiful sword fight scenes I've ever seen. It's definitely worth watching and studying:
There a bunch more ways to deliver an action scene. ErithEl has mentioned a couple of good ones: overhead view and view from below. There are also ways of making your character look increasingly outnumbered, and ways to make your character's foes look like chumps even before delivering a blow. It all depends on the intent of each panel because really, the action does all the talking.
(I'm so sorry that I'm mostly using sword fights as examples ;A; )