There are lots of lightsabers:
-Double-sided: a lightsaber with blades on both sides. Some can be taken apart into dual lightsabers. Some models can fold up. Typically longer than a normal lightsaber. Can be used as a long-handled single bladed lightsaber. Some notable examples of use were by <PERSON>, <PERSON>, <PERSON>, and Jedi Temple Guards.
-Dual: Two lightsabers, normally alike. Some can be put together to make a double sided lightsaber. Some notable examples of use were by <PERSON>, <PERSON>, <PERSON>, and <PERSON> (just for a short time on the Trade Federation Control Ship).
-Crossguard: A single-bladed lightsaber with two mini-blades protruding from each side of the handle, normally making it slightly longer than normal. Better for blocking enemies with more saber range. A notable example of use was by <PERSON>, though a few ancient jedi and many ancient sith used them.
-Shoto: A shorter version of the lightsaber, with the handle a few inches shorter and around a 2 1/2 - 2 foot long blade. Some notable examples of use were by <PERSON> and <PERSON>.
-Lightwhip: A type of single blade lightsaber except the blade was like a whip, so only extremely skilled Jedi or Sith could wield it without killing themself. 569
I don't know of anyone who uses them, though.
-Spinning: A double sided lightsaber that can spin on a track built into the handle, so it basically spins automatically. It can be used as a single-bladed spinning lightsaber, though, too. Some notable examples of use were by The First through Thirteenth Sisters (Estimate) and the First through Thirteenth Brothers (Also estimate).
-Dual-Phase: A lightsaber that uses two Kyber Crystals, therefor being twice ac long. Some dual-phase lightsabers can be switched between 3 feet and 6 feet. I don't know of any users of this blade.
-Curved hilt: A lightsaber with a curved hilt, enabling much more maneuverability. Sometimes used as dual and dual curved hilts can be combined to make a double-sided blade with an S-shaped handle.
-Blaster-Saber: A lightsaber with a blaster attached, enabling you to have a compact weapon. A notable use of this type was by <PERSON>.
-Underwater-Saber: Most lightsabers short out when they touch water, but underwater sabers don't. The only known one was used by <PERSON>.
-Lightsaber Pike: A type of lightsaber, typically with a very long hilt, long than a double sided hilt, and sometimes a longer or shorter blade. I believe some Jedi Temple Guards used them.
-Darksaber: A lightsaber with a rectangular prism hilt instead of a cylindrical hilt. The blade is shaped like a sword's blade, and is a black flecked with white color.
-Normal single bladed: Most jedi and sith use this. It's in balance with all the pros and cons.
There are others that I haven't covered here, but I believe I got most of them. 537