The best typos, of course...
Are road signs. Both the ones stuck on poles and, especially, those painted on the road. I'm sure we've all see the news reports, or experienced them at some stage so I'll leave for others to relate any especially good ones. Although IIRC there was one where someone needed a sign translation into Welsh, emailed the translator, got an Out Of Office Reply, thought that was the translation and duly had the sign made up and installed.