While Digikam needs a database, it comes bundled with showPhoto (I have v 4.0.0beta3 right now, don't know if showPhoto was available in earlier Versions).
showPhoto is a standalone image viewer, without database. It displays pretty much the same metadata as Digikam does.
This is a good option for someone who needs both: indepth asset management and a quick viewer with editing features...
Personally I can recommend Gwenview, too. Metadata display can be fully customized and it displays every kind of data.