I wrote a tutorial on how to do it here.
http://pi.shockingtales.com/tuts/lightsaber.html
Basically you have to move both points of the lightsaber emitter every couple of frames, moving one point to the base of the fishing rod, and one to the tip. If the blade ever goes behind an object or the actor, you have to use Blockers to hide the blade.
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Elvis Deane!
The particleIllusion FAQ
particleIllusion Resources and tutorial CD
Astounding Adventures