Applian FLV Player
If you require a simple way to play FLV files and none of your other media players seem to handle that format, Applian FLV Player is an option.
Although this product is free, there are additional programs such as Replay Converter that it may ask you to install. Replay Converter is not free, so choose not to install the additional bonus software if you are simply looking to play FLV files with Applian FLV Player.
Note that VLC Media Player can also handle the FLV file format.