Which one do you prefer? Gomu Gomu no or Gum Gum? To be honest, I found myself more comfortable saying Gum Gum Pistol or Gum Gom Bazooka rather than Gomu Gomu no Pistol.
I know it was made by the dub, but it's literate translation, you know?
Prepares flame shield
And BTW, if you watch the Chinese dub, then you will never hear Luffy yell, "GOMU GOMU NO…!" either.