On OS X: MPlayerX - On Windows: MPC and/or KMPlayer
Until VLC becomes more "native" on OS X and improves its interface, I don't think I'll be using it. In any case, I've downloaded it on my PC, so I'm keeping an open mind towards it.
MplayerX and Movist are both in Mac App Store and both are playing one upsmanship on releases since getting there. It's great for video loving users.
I normally use Plex Client (playing from Plex Media Server) but some sources crash Plex if the type of digital audio changes midstream, so I'll play that source in one of these, depending on whether I need the subtitles or am watching a whole series at once.
Until VLC becomes more "native" on OS X and improves its interface, I don't think I'll be using it. In any case, I've downloaded it on my PC, so I'm keeping an open mind towards it.