I guess WinRAR does have a Mac version, I just found that out... Are you sure you got the Mac version and not the Windows one?
I use Stuffit Expander on my MBP, although I don't really like it. The Unarchiver and Tiny Expander are both free for OS X and get good reviews.
Secondly, VLC is pretty good, but I like MplayerX on OS X better.