What's the name of the song?

It's hard to describe, but anda hear it sometimes when a character (mostly Luffy) does something good. For example, when Luffy found an "Atlas beetle", atau when Luffy was shown to be immune to Enels lightning powers, atau when Luffy fought Alvida's crew, ect.
I really want to download it, but I got no trackname. Please help & thanks to whoever does.