MKV Player

Generally, MKV files are quite difficult to open as most video players don't have the capability of playing and decoding Matroska files.

One solution would be to try to convert them to a more manageable format but this can be a time-consuming process. A simpler way to solve this issue would be to use a player that was specifically designed to open this type of files, a tool like MKV Player.

To tell the truth, MKV Player doesn't make you impressed at the first sight. It's basically a common player with a design which is, in some ways, similar to an older version Mplayer. Another thing that I didn't like was the fact that it continuously plays your video clips in a loop (default setting) and you have no way to change this.

Also MKV Player has a few handy options like allowing you to easily capture screenshots from the video that you are currently watching or offering you a simple way to adjust the timing of the subtitles. Furthermore, you can also use a playlist feature to create and save lists with the movies and videos that you want to watch.

I would only recommend MKV player because it can play MKV files (obviously) and because it doesn't cost a fortune. It doesn't have any settings or preferences menus, it has a rather mundane look so I would surely not make it my default movie player.