I’m no Flash expert, so generally if I’m dealing with Flash it’s Flash movies, which are .flv files. However, some people might need to insert Flash objects into their posts or Pages, and these files have the .swf suffix.
Someone on a forum recently was on a search for the easiest and least destructive way of inserting .swf files in their posts, and their conclusion was that the Kimili Flash Embed for WordPress plugin was the best option out there.