MediaPlayerLite is great for opening mpeg, mp4 and avi. I’ve also noticed you can also play DVDs really easily. Would recommend MediaPlayerLite for playing any video file and any random audio files like FLAC or AIFF.
MediaPlayerLite seems to be able to play any file I throw at it. It opens the ever popular MKV (Matroska) for your HD files, and also MP4 files that iTunes seems to love. I’ve also used it from RAM (Real Movie) and QuickTime files.