- "Don't taze me bro!"
- ―Mace Windu to Palpatine during their duel
Force lightning was a Sith Force power that hurts like hell. A subset of Force weather control, almost every Sith Lord that ever lived used this power because it made them look very cool and evil. However, when n00bish Sith tried to perform it, it was actually quite nice and ticklish, as demonstrated by Palpy on the Death Star when he tickled Luke Skywalker with Force lightning to the extent that he almost died of laughter. It was also used by the most awesome Sith ever, the girl on Cocaine, and Count Dookie. It was also used as a cheap but unpredictable alternative to microwaves.
Examples of Force lightning
The most common user of this extremely cool, wicked power was of course Palpy, but then again his assistant copied his master's plans and became one of the Sith, therefore gaining Force lightning to his advantage. Technically, all Sith could use Force lightning, and so to a lesser extent could that old horned geezer, but of course nobody paid any attention to him. Many, many examples of Force lightning have come into being during the history of the Galaxy. For instance, perhaps the most famous incident is when, after Alderaan was destroyed, Darth Vader sat back and used his powers of Force lightning to prepare himself a steak. Many wondrous abilities come out of this unique power, and only the Jedi scum have even come close to dissing it.
Luke's technical incident
Bounty hunters demonstrated the use of Force lightning too. When Luke kept on pissing off Han Solo during his test run on their escape from that big ball, Han Solo got so infuriated at the annoying little brat's constant whines that he eventually levitated him six feet and tickled him with Force lightning to get him to shut the Hell up, and then immediately said 'From now on, anyone who whines on my ship gets a tickle of that. This goes to show that Force lightning was not limited to Sith alone.
Attack on Tatooine
Many people now know that the fact Luke lost his foster parents was his own fault (as portrayed in Pants Wars Episode MMIV: A New Pant). Indeed, he possessed the ultimate power (Force lightning) all along. If only Luke hadn't gone along to rescue R2-D2 but had in fact remained in the farm and milked blue milk, then perhaps he would've managed to prevent the stormtroopers from barging into the place via his amazing powers, and also he would've definitely been able to make the Stormtroopers laugh as they invaded. Force lightning was described by some victims as "hilarious". No wonder Palpatine used it.
Father and Son
When Darth Vader battled his annoying, pathetic wimp of a son he realized the large quantities of power that Luke immediately had at his disposal, including Force lightning, and he ultimately realized the main reason that Palpatine wanted to make him a Sith. So for that purpose, Darth Vader lured Luke out under the pretense of M&Ms, and therefore Luke willingly complied. Darth Vader already knew what a fool his son was, and therefore this plan was as easy as Hell, so Luke emerged and was tickled to Death by the Emperor. The Emperor won, thanks to his amazing powers of Force lightning, (and after all, being a senator, he was charged with making ridiculously serious speeches daily, so he was just practicing using the power on Luke to cheer himself up) but he succeeded in making 'Yo Mama' jokes about Darth Vader's wife, so Darth Vader picked him up and tossed him into a pit. So allegedly the power of the Force lightning died...
...Or so you think
But it lived on in Luke! For as we all know Luke was the only Jedi in the Galaxy with the Supreme Power: oops there's a big secret there, maybe I shouldn't have told you, oh, it's too late now. So Luke was free to carry on the genes of a Jedi. After the Empire fell, Obi-Wan, Yoda and Anakin caught him in the act, which meant that Anakin was obviously proud his power remained.
Darth Jawa used it to power his Juicer once, and Darth Elmo used it to light his cigarettes. It was a very powerful Force power; if used correctly, one would be able to kill many people, which is what the Sith used it for. The Jedi were known to use it to "help" people. They used it to power an entire city once, but the planet was destroyed by Darth Darth Binks' private planet destruction team, Sesame Street, hours later. Darth Darth Binks did not like how the Jedi used the Dark Power.