Which Movieplayer are best for Raspbian?

As topic.

If the player need special actions beyond the normal apt-get-thing I would like to know that too.

Anything else I need to know?

Depends what you mean by "best"?!
I believe omxplayer is still the only movie player outside of XBMC that has hardware acceleration? (I could easily be wrong, it's not something I've been following)
But for low-res video, there's probably plenty of other choices.

[mahjongg]

the latest raspbian with hardware floating point support has a player built in that is one of the few that uses GPU acceleration, which makes it an automatic "best", as software decoding with the 700mHz ARM is unsatisfactory to say the least.

How does one use this built in player that you speak of?

I believe the player is called OMXplayer and needs to run from a command line.
I haven't tried this however since I don't have a video to test so I might be wrong on this.

Nimphina's answer is correct. Just type omxplayer to the command line.
other essential commands (used during playback):
q = quit
p = pause
forward key = skips a bit
backwards key = skips backwards a bit

Regarding omxplayer... is there any way to insert subtitle files to the omxplayer without having to insert the subtitles to the file itself? If there isn't... is there a player that is able to run 480p/720p-videos, where you could do that? (I am guessing no, but better safe than sorry).

Regarding omxplayer... is there any way to insert subtitle files to the omxplayer without having to insert the subtitles to the file itself?

Dunno.

If there isn't... is there a player that is able to run 480p/720p-videos, where you could do that? (I am guessing no, but better safe than sorry).

AFAIK the CPU in the Pi isn't quite powerful enough to software-decode 480p videos, and (again AFAIK) the only player that can use hardware-decoding is omxplayer.
But I guess XBMC might be worth a look at, if you haven't already?

Another option is to have a separate SD card with XBMC as the player.

See the thread here http://www.raspberrypi.org/phpBB3/viewtopic.php?f=56&t=11546 for the OpenELEC and DarkELEC systems.

These run like a dedicated media player with little to no access to the underlying OS, but it depends on what you are trying to achieve and how easy you want to make life for yourself. I like being able to throw in a different SD card, have a 15 second boot and be presented with a nice interface to select and play videos. My other SD cards have OS versions for programming and tinkering. This way I know I can watch a video no matter how much experimenting I have been doing on my other SD cards.

Another option is to have a separate SD card with XBMC as the player...

I think this will shorten sdcard slot life. Probably some kind of hybrid image ( Raspbian/?ELEC/something similar) would be better idea.

But if using the xbmc how can I install network resources?

Then I would like to mount my samba stuff (win7 network drives etc.) to the xbmc image's file system?

Does the xbmc have a shell included so I can install all the necessary stuff using apt-get?