Flash games are not always the best in terms of graphics but they're fun, fast and importantly, usually completely free.
The downside is that you always need a web browser and a connection to the internet to play them. Not so with iSwiff however. iSwiff allows you to play Flash games, animations and movies without your web browser or even a connection to the internet. Of course, you need to be able to download some Flash games but once you've done so, you can play them to your heart's content offline, within iSwiff. You can find plenty of games on the developer's website plus a search for "Flash games" or ".SWF files" in Google returns thousands of results.
You can play either in single screen or full screen mode and not have to worry about toolbars and ads getting in the way of your gaming experience. iSwiff works with any .SWF file and uses Adobes's Flash web plugin for playing movies. To open a .SWF file, simply drag it into the iSwiff icon or use the file menu in the top left of your menu bar. In the "Window" menu, you can switch to full-screen mode or simply drag the window to the size you require. You can use Cmd-F to exit full screen mode or just move your mouse to the top of the screen where the menu will appear.
To exit "full screen" move the mouse to the top of your screen and the menu will reappear. Or hit cmd-F.You can also just hit cmd-Q to quit iSwiff. Perhaps the only downside of iSwiff is that the developers warn it may not work very well with .SWF files that use newer Flash innovations.
It would have been nice to have had a few auto-links to Flash games built into iSwiff but apart from that, there's no faulting it in a great offline Flash gaming environment.