I heard recently that Arnie offered to do the voice for the Terminator in the German dub of the film of the same name. They said no because his accent made the killer robot sound like a farmer or country bumpkin to German ears.
Honestly, his accent in German is hilarious. I dug up some old YouTube footage of him in German a while back and he sounds ... cute. Definitely not hard-core like he does in English. ;-)