I haaaaaated 'Believe it'. Dattebayo is so much better, especially because it's a verbal tick that he got from his mother, who is adorable and I love her.
0. I've seen several characters use the archaic "de gozaru". Can't think of their names right now and should be focusing on my algebra homework, though.
But Naruto isn't your ordinary ninja-ttebayo! And hell, it's good to break some traditions, like how season five of Digimon broke the goggles tradition.
"Gum Gum" is what Luffy says before each attack~ Kinda like with Natsu/Gajeel/Wendy saying "Karyuu/Tetsuryuu/Tenryuu no".
I'll sometimes say "uu" or "uryuu" irl. Uu was prolly inspired by Maria from Umineko and I now cannot say "uryuu" without thinking of Uryuu from Mirai Nikki o3o