Barrel

 is a gun which fires fish that have a chance to stun enemies and leave pools of water.

Trivia

 * The gun used to be able to synergize with 38 Special, M1911, or Derringer for the synergy.
 * Is a clear reference to a book of a similar name written by Dr. Seuss.
 * The gun itself as well as its flavor text are a reference to the idiom "Like shooting fish in a barrel" describing an effortless or simple action, with guaranteed success.
 * This gun's quote in Portuguese, "Isso, Isso, Isso", is a reference to a popular Mexican TV show called El Chavo del Ocho about a boy who lives in a barrel.