What's the name of the song?

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