MPlayer OSX Extended[1] is your friend. It has playlist, it has nice interface and you could swap out MPlayer player binary with a newer one (e.g. mplayer2-git[2] or build your own via Homebrew[3]). I like MPlayer OSX Extended far more than MPlayerX or any other alternatives, shame that it didn't get the attention it deserves.

[1]: http://www.mplayerosx.ch/

[2]: http://code.google.com/p/mplayerosx-builds/downloads/list

[3]: https://github.com/pigoz/mplayerosx-builds/