QuickTime Player can be used to present .swf (Flash) but it has some limitations.
In the "publishing" phase from Flash you must chose Flash 5 (or lower). These files can then be opened and saved as .mov format.
Since Flash is a "muxed" format (audio and video in the same track) you can't use these files in other Apple apps because the audio track can't be extracted from the video and only the video will be converted.
QuickTime .mov files can have up to 99 "tracks" and you can get a wacky mix of audio and video into just one file. An example of one of my "Flash to QuickTime" conversions made in 2002:
http://homepage.mac.com/kkirkster/xmas/index.html
Other uses of Flash would be buttons or controllers in "skin" track QuickTime movies. Another example of one of my pages:
http://homepage.mac.com/kkirkster/MTV/
Hundreds of ways to "mix and match" for interesting Web pages.