Know any "unrippable" games? I'm great at breaking things

[MakutaMaster962]

The PS3 version of The House of the Dead 4 uses the .cno file extension for its models. I know because I've already ripped a lot of sounds from the game, as well as a few textures and some models. But the process of converting the models to a more useable file format is pretty much impossible(for me, at least).