Apple QuickTime is a very well known software and it also supports H.264 playback. In fact, high definition QuickTime clips are all encoded in H.264 (main profile), and the Pro version of QuickTime allows you to encode to H.264 as well.
Like Nero ShowTime, QuickTime is only designed to play back files that has been encoded using QuickTime (Pro), and so, compatibility is not the best.
Pro: Easy to install. Good player interface. Pro version allows encoding and conversion functions.
Con: Poor compatibility with non QuickTime encoded H.264 files.
Instructions: Apple QuickTime Download Links.
$69.95 (Deluxe version only)
PowerDVD is one of the world's most popular media players. In the latest version (7.0), PowerDVD Deluxe includes a built in H.264 decoder, which also supports ATI's Avivo video acceleration (available for Radeon X1000 series cards).
Compatibility is fairly good, with several files unplayable in VideoLAN, Nero ShowTime and QuickTime all playing well. Performance was only average.
Pro: Easy to install. Good player interface. Very good compatibility.
Con: Only average performance.
Instructions: PowerDVD Download Links.