In the prison scene, when Spike recalls the deal he made to Electra, his dubbed voice doesn't match the amount of his "mouth flaps". In between his voice can be heard, and then nothing when his mouth is still moving.
Spike's bullet wound when he fights Vincent on the tower.
When Spike chases the Moroccan out of the shop, and is searching for him in the crowd, his jacket jumps about between shots.
Spike's hair changes from green to black repeatedly throughout the movie.
Numerous grammatical and spelling errors on computer screens (this was a loose translation by the Japanese crew).
During the opening credits, "Editor" is mispronounced as "Editer".
The name of the city all it's happening appears to be "Alba City" like it's written on the floor by the near end when the mayor opens the Halloweens celebration, but before that when Jet is trying to get the airplanes, behind the guy who rents them it says everywhere Alva with a "v" instead of "b".