VLC for Mac.
I find it really cool, but not without its flaws.
For example, when I add a folder to the library, it only acknowledges the video files and not the subtitle .srt files. But if I add the files directly, then the subtitles get on the library as well.
Also, is it possible to automatically set a media folder to be its library? I keep a folder on the desktop for that, it's a "temporary" folder excluded on Time Machine, just for my media necessities on the go. I can't find any option regarding that.
Another gripe with it is that I can set different types of fonts for the subtitles but it seems to be completely indifferent to any bold/italic/size/color settings, it always shows the same.