Trigun
A pair of humanoid twins were brought along during the Project Seeds expedition. They were named Vash & Knives and they grow at an alarming rate under the guidance of Rem Saverem, Vash and Knives were taught about the need for humans to love and cherish life so that what happened to Earth will not happen again.
After many years, Vash learns of a scientist researching the lost technology. Vash then journeys to July to give the scientist the results of Rem's research. When Vash and Knives have seen each other, Knives shot the left arm of Vash. The gun blogenetically transform into a huge weapon. Then it destroyed the town of July.
A bounty of 60 billion double dollar is put on the head of Vash - known as Vash the Stampede, the humanoid typhoon.
Well, I hope I didn't spoil the series too much for you, but believe me the ride is worth it. Trigun will make you laugh, cry, shiver and even contemplate on morality. It's hard to find anime like this these days. Love and Peace! 
