One deceptive lightsaber component could rule lightsaber fighting
If the user kept it secret and made sure it was only used to kill, then he/she could prevent others from finding out about it.
What I'm thinking is a saber with a pressure-sensitive "kill switch" that physically stops the blade, either by diverting it into the hilt or simply cutting its beam power, causing the blade to instantly vanish instead of "retreating" into the hilt like when they're shut off.
Releasing the kill switch would of course make the blade reappear instantly.
Practice the timing, and this could be so deadly. Have a saber battle for a few moments, make a killing swing, your opponent blocks it.... And right before the blades make contact, hit the kill switch just long enough to pass your opponent's blade.
Then release the switch and finish your swing on the backside of the blocking blade, killing your opponent. If the kill switch is used fast enough, it would look like your saber passed through their saber.
Kylo reminded me of this when he switched on his saber for just a moment to kill that one Praetorian guard through the head. It's the first time I've seen a lightsaber blade blink on and off so quickly.