The worst OP Dub (and fansubs, lets not forget that they fuck up too.) were when I read the article on the OP Bootleg on SA and they said Usopp was called "Crock Bu" and Sanji was "Sunkist". I have also seen various fansites translate them wrong, including such horrors as:
Luffy=Lu Fei, Monkey D. Louie, Roofy, Lufiey, and even "Rubba" (WTF)
Zoro=Zorororo, Zowlow, and Zorlow
Usopp=Yusoap, Usoppou, You Sopp
Nami=Namu
Sanji=Sanshi, Senshi, Sungee
Choppa=Chopat, Chofur
Captain Kuro=The Black Captain, Captain Claw, and Seargent Kuro
Gin=Jin, Gene
Pearl=Pool, Pull, Paru (Which may or may not be Romajii but still.)
Nico Robin=Neko Lowbin, Rabin