A free app for Android, by BlueRingApps.

Keepvid is the best HD movie player app to play & watch movies on your phone. It is an app that will play any type of video directly on your phone. All formats are supported, including MKV, MP4, M4V, AVI, MOV, 3GP, FLV, WMV, 3gp, etc. It also plays all the most common video formats. 

The app is very simple and easy to use. The interface is very user-friendly. You can search for any movie or video by name. You can also watch your favorite movies or videos in the Keepvid app.