#1 – VLC 2
#2 – XBMC
#3 – Plex
#4 – Perian
#5 – MPlayerX
Hard to say which is the best, but since they’re all free, there is no reason not to try them all and discover which is the best for your specific needs.
Plex and Kodi are good. Also, check out Universal Media Server.
I always use iTunes. I think it's the best media player for now.
I prefer Elmedia Player. It's a media player for Mac OS X which supports almost any kind of movie format. Also, it's absolutely free. So, highly recommend https://mac.eltima.com/elmediaplayer.html.