You can configure Raspbian to play a video in OMXplayer when you double-click on it by right-clicking on the video, going to open with, and selecting custom command.
Under Command line to execute: enter, omxplayer -b
Check, Execute in terminal emulator
Add an application name, and check Set selected application as default action for this file type.
You will have to do this once for each file type (mkv, mp4, avi, etc...).
After that, double-clicking on a video will launch it full screen in OMXplayer. Hit "q" to quit playback early. omxplayer --help, or man omxplayer for more info.
There is also an OMXplayer GUI application you can install.
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?