MPlayer ist just great. It supports every codec I tend to use, it doesn't depend on external librarys and it's stable like a rock. It also supports full-screen playback on sophisticated dual-screen setups with an additional TV.
AMAViS is feature laden tool that provides a fantastilion features. Unfortunately it is very diffficult to configure, takes far too many ressources and has an very questionable coding style. It provides as an excellent example how your Perl code should not look like.