Movist is a strong VLC alternative for Mac
Though Macs ship with a reasonably good video player in the shape of QuickTime Player, the sheer number of different types of video files that are available out there can be frustrating to keep up with. You have to install various plugins to make QuickTime compatible with them all. Or, you can choose an all-in-one solution like VLC.
Of course, some people are not fans of the look and feel of VLC. If you're in that camp, check out Movist. Movist is another all-in-one video player for OS X that has so far handled every file type that I've thrown at it. You can even go into the preferences and manually control the decoder that you want to use for each file type in case one works better than another.
Movist's UI feels very at home on my Mac, and I like it enough that it has become my default video player. I'm looking forward to see what the next update holds for Movist, which appears to be a very active project hosted on Google Code.