Some people are "obsessed" with using quicktime which is why I mention how to do it there. And eventually I won't even be able to recommend getting Perian since its developers are stopping support on it (read statement at the link I gave). Get while you can anyhow just in case.
Personally I would use vlc and I recommend it (although I still use vlc 1.1.12, the newer and current vlc 2.0.1 has a few growing pains but pretty much works). I use it strictly for video playing because it has options most others have. Turn on it's advanced options you will see settings for practically everything under the sun related to video and the audio tracks.
One vlc option (a preference setting) I like is that I don't have to move the vlc movie player on to the screen I want to play full screen video on. Most every other video player, like flash in a browser, expands to full screen on the screen it's video window is currently on. When I enable my TV for video, I can click the video to open vlc and it starts playing full screen on my TV without me having to do anything. I don't have to move any windows off my main monitor.