If you want to watch some MA (Mature Audience) Ninja fighting action then Basilisk is an awesome anime to check out (HULU both Dub & Sub available). The story is about a decision to base the next Shogun on whoever from the competing families of the Iga and the Kouga (10 Ninja’s from each) can be last left alive. At the heart of the story it is much like Romeo and Juliet in that the head of each family is in love with the other (Gennosuke (Kouga) and Oboro (Iga)). It is very violent though, so you have been warned!!!
There is also a Live action movie version of this anime which is also pretty good and called: Shinobi: Heart Under Blade