Fire
Fire was a way of life for the Village Hidden in the Leaves. Not just through their Hokage or their Will, but through the individual people. The battle for cigarettes between Shikamaru and Temari (Her stealing his lighter was a common occurrence). The way that even in a world with Electricity so many people used candle light. That the most powerful combination attacks of Team Seven revolved around the combination of Amaterasu and wind to create Blazes so huge they could obliterate armies.
And it wasn't just the physical manifestation of fire, or the philosophy of the Will of Fire which made it way of life. It was the people. A passion burned through their veins unlike any other. They were everything which fire was. Wild, yet controlled. Fierce and ferocious. And when you set them loose on the enemies of Konoha . . . Very little could stop them.
Fire wasn't just a way of life, it was their way of life.
Coincidentally I just started watching Fairy Tail.