Adobe Media Player
We are listing this merely to make you aware of it's existance. We have no information as to its accessibility.

FooBar2000
FooBar 2000 is a very configurable media player. It allows you to set multiple navigation hot keys readily. It appears to be very screen reader friendly. However, this is probably not for the beginner.

VLC Media Player
Open source media player, will play most files.

VLC Media Player Hot Keys
VLC Media Player Hot Keys.

Win Amp Media Player Hot Keys
Hot Keys for the Win Amp Media Player.

WinAmp Media Player
Home of the WinAmp Media Player. Screen reader usable, but not especially friendly.