A while ago MaketheLogoBigger posted The great Art Director Escape, and I see now that adding funny subtitles to this film has become a bit of a meme like LOLcats. Der Untergang is a thoroughly impressive depressive movie where Bruno Ganz portrays Adolf Hitler so realistically you'd think it was a documentary. I saw it twice in the movie theatres, once without subtitles (and I don't speak German!).
Here are a few more - do you know of any others? Add them in the comments, y'all.
Hitler banned from iSketch
Hitler banned from XBox Live
The downfall of HD-DVD.
Thanks reformedjerk at metafilter for showing me more.