Lightning would be cool! Here was my idea of it: the lightning would be a white bolt that comes down from space during any rainstorms and hits the tallest structure in a 25 block radius of its origin point. Basically, it would be a streak in the background that came down until it found something within 25 blocks of it.
If it hit anything electric, it would help fuel it for a little bit. The streak would be in the same background level as wire, but could also interact with blockheads and conductors.
If it hit a blockhead, it would freeze them for 10 seconds, then temporarily boost all of their settings. Depending on how high up the blockhead was, it would boost the settings for a different amount of time and later cause a different amount of damage. The higher up, the more boost and more damage. There will always be a 5% chance of instantly dying when hit by lightning. You can heal a lightning injury by eating food or sleeping after the boost wears off. If it hits an animal, they die. If it hits wood, the wood burns into flames.