MPlayer is a neat program if you need to do other tasks on videos than just watch them..but it doesn't integrate too well to the desktop, not as well as Totem does, anyway. I think the only codec packages you need are the GStreamer ones; that is, if your Totem uses GStreamer as it's backend (totem-gstreamer vs. totem-xine which uses Xine as it's backend).
It's a shame Fedora doesn't handle this as easily as Ubuntu does, not yet at least. On Ubuntu, if you open a media file that there is no codec for yet, the player app asks if you want the packaging system to search for one, and if such a thing is found (needs an internet connection, of course), it's installed. For the usual formats this is the case, so it's pretty trouble-free for the user. Fedora is slightly more 'cautious' about these codec things, and that means extra work for the user (adding a new reposity, fetching the right packages, ...)
Another option is to replace the GStreamer-based Totem (totem-gstreamer or equivalently named) with Xine-based Totem (totem-xine or similar) and install Xine's extralibraries (libxine-extracodecs or xinelibs-extras, can't remember how it was named in Fedora packages). Very same thing as GStreamer, but with a different backend. If you can fetch GStreamer plugins (codecs), though, that's unnecessary trouble.
MPlayer, VLC Player and such are a great addition for some formats, especially VLC player, but as long as you don't need them, I don't recommend installing them. They're just a bunch of extra disk usage and extra menu icons in the system, and make it look more bloated than it needs to be.