With the release of Iron Man 2, we'll be able to add Mickey Rourke to this list.
Great actor, ....but horrible Russian accent, ...although it was a very valient effort.
oh... pretty much ALL the Jamaican accents in 'Cool Runnings'
A friend of mine was both the photo double and the stunt double for one of the actors.
He is Jamaican, ...and I don't know how he kept a straight face throughout the entire shoot.