Here is a short tutorial on how to create a lightsaber effect in Photoshop. This is actually one of the first tricks I was taught in Photoshop and despite a whole lot of new features and upgrades in Photoshop over the last 15 years, this is still my preferred method for creating a lightsaber!
Download assets for this tutorial here.
BONUS: The download assets includes the layered PSD of the composite (something I usually do not include).
I used a flare in this composite from my Lens Flare pack, which you can check out here.
I also used two light leaks. You can see the full pack here.