Definitely a Pikachu.
That little bugger will break through anything, and it's invincible as long as you can repeat the word "Pikachu, dodge it!" fast enough.
On the aesthetic side, I prefer shotguns, whether is those double-barrel shotty, classic pump-action, drum magazine shotty, or whatever kind anyone comes up with. I'm a sucker for the "Boom!" it produces. (Must be the barrel sized).
ps. I remember reading in some other thread where someone goes on a nerd rage about sawn-off shotgun being physically impossible, as the recoil would be too great for human to handle. I'll let you know that in my country, we have single-load homemade shotgun "pistol" smaller than your average revolver. They're called Thai Pradit guns (direction translation: Thai made). Apparently it was THE SHIT about half a century ago (Our equivalent of the wild wild west).