There are a few that manage to stand out from the crowd among the wide selection of media players.
The list of its handy features is quite long.
The rotation is applied in real time without affecting the actual video orientation.

If you shut the video and then play it again, the orientation goes back to normal.
By default the screen rotation is triggered by mouse click.
Optionally, a shortcut key can also be assigned to each of the rotation commands.

By enabling this option, you dont have to rename subtitle anymore to match the title of a video.
The same setting can also be applied to audio files.
Almost every single command can be executed by pressing a pair of keyboard buttons or even a single button.
What is even more amazing, each of these shortcuts are customizable.
This is the one area where KMPlayer beat down GOM Player severely.