On Snow Leopard i used Movist all the time. It was a light-weight ffmpeg player that played anything and everything I threw at it. It seems to almost be abandonware though as it hasn't been updated in over a year. So of course it doesn't adhere to any of the Lion standards and it's windows can't even be re-sized except from the lower right hand old-style mac. It also seems to "freeze" once in a blue moon with Lion for like a quarter second. I tried MplayerX, which is on the App store and that seems to work okay, but some of my video files...such as some, but not all AVI files...seem to muck up the works. For instance some movies I can't fast forward on, it just snaps back to the beginning and messes up the sound a bit. Or if I try to slide it forward half-way, it just freezes the movie. I would use VLC, but I don't like the controls. No matter what I do, I can never ever ever ever get it to work with my arrow keys. I just like hitting the right arrow...by itself, no modifier key...to skip ahead 10 seconds, and then the left arrow to go back 10 seconds. Both Movist and MplayerX do this. (well, not always with MplayerX due to the problem above). In VLC, I've tried and tried to make it do that just using the arrows, but it won't work. Or else I fail at preferences. So this also leaves out using Perian with the normal Quicktime player, as that doesn't really do anything either.