I have been using This Player since I Brought my Smart phone. Its free of all but you have to purchase the pro version. You can get this app on Play Store. It has great features and You can watch Any HD video With MX player. I recomended MX player for Video playing. it plays any Format like mp4 avi 3gp mkv mp3 etc.
And you can also set themes on MX player With cool look. Its totally offline and you can play video from your Internal or SD card. Its a good App And try it now and enjoy watching video on MX player!