If you could use a Non Star Wars material in a lightsaber...

What would it be?

Kryptonite, that way I get a cool green looking lightsaber

a green lantern ring. Sweet lookin green lightsaber and i can use it with my WILL

Cyttorak's Gem! ;)

I was about to say that,

Casing made of adamantium

The Cyttorak Gem, and Mind Infinity gem as focusing crystals, giving me a badass dual phase purple lightsaber, along with the other benefits C's gem and the Mind Infinity Gem give their owner....

Attach lightsaber to batmans grapple and launch it at people.

I always tried thinking m'kraan, until I realized, hey, that's too big to fit in a small lightsaber...