Sodom

Sodom (ソドム, Sodomu) and Gomorrah (ゴモラ, Gomora) are the two gigantic King Bulls (sea horses in the most literal sense) owned by the Franky Family.

Past
According to Chopper's translations, they were found by the Franky family in the stomach of a Sea King they were eating, and they were too full to eat the sea bulls too.

Enies Lobby
Sodom and Gomarrh take the Galley-La, Straw Hat Pirates and Franky Family to Enies Lobby. Once there, the Franky Family and Straw Hat Pirates use them navigate their way through the island and past any Naval or Government forces that try to stop them (allow with greatly assisting in the battle against the Giant guards).

Unfortunately, Sodom is felled by a mortar shell (but tearfully begs the others, through Chopper's interpretation, to go on without him), and Gomorrah is taken down soon afterward by cannon fire. However Gomorrah, fueled by memories of Franky taking him and Sodom in and looking out for the two, manages to summon up his last ounce of strength and crashes through the Enies Lobby courthouse's courtyard before finally passing out from the pain. Without their assistance, the Franky family managed to make it as far as Enies Lobby's courthouse before being tied up by the Marine. The two were scooped up by Oimo and Kaashii and joined the Straw Hat Pirates allies' rush to escape and were loaded onto the Puffing Tom and brought back to Water 7.

Aftermath
Two days after the destruction of Enies Lobby, they are now back on their feet and well enough to join the Straw Hat Pirates' victory party.

Trivia
They are named for the cities of Sodom and Gomorrah, which (according to the Bible) were famously corrupt.