VLC for Fire
VLC for Kindle plays most local video and audio files, as well as network streams (including adaptive streaming), like the desktop version of VLC.
VLC for Kindle has a media library for audio and video files, and allows to browse folders directly.
VLC has support for multi-track audio and subtitles. It supports auto-rotation, aspect-ratio adjustments, hardware acceleration and gestures to control volume.
It also includes a widget for audio control, supports audio headsets control, cover art and a complete audio media library.