It's hard not to make a play on words or a pun when talking about 1 Flash Gallery, because it is what it says, and adds what it is, and really makes your site flashy. (Sorry, I couldn't resist.) The most popular gallery for WordPress is the NextGen gallery, which is excellent, but this is something quite different.
If you've been looking for a way to put up eye-catching galleries, Flash is one way to go. 1 Flash Gallery is a plugin that will provide Flash galleries for your WordPress site.