GIF Viewer V2.1 by David Jansen is one of the best freeware gif 87a viewers for the C64.  If a gif file was not created from a Commodore C64 or C128 graphic, often few colors are displayed.  The commercial program GoDot for the C64 has a gif decoder that often displays more than 3 times the number of colors than GIF Viewer V2.1 for the same gif file.  The main advantage of GIF Viewer over GoDot is it views interlaced gif files.  GoDot can view non-interlaced gif 87a and gif 89a files.  The patched version +VGIF64 can view both gif 87a and gif 89a files.  The files viewed can be saved as either Koala format files or Doodle format files.