There is only one file type that uses the .VP6 extension:
TrueMotion VP6 Video File
Encoded video format developed by On2 Technologies; used primarily for Internet video and Flash video files; supports multi-pass encoding, constant or variable data rates, and advanced error recovery; can be used to encode high resolution video, including 1920x1080 HD video streams.
The video format used by Adobe Flash Player 8 and 9 is based on the On2 TrueMotion VP6 codec.
Updated: November 17, 2010