Alright, in the past I have messed around with a few games attempting to get models / textures / etc out of them. I'll post what I've actually accomplished with examples and what I used to do it. Please to be posting your own as well, and maybe we can collaborate and bust open a bunch more games.
First, a quick and simple one, Sonic Jam for US saturn. You can get the art gallery images out by using a japanese art program called
Susie, and giving it
this plugin, which will let it read saturn .dg2 files. The art gallery is in .dg2 format, and should be simple to find on the disc.
Sample:

Next up is one I had massive trouble with but eventually managed to get help from people who actually knew what they were doing, and thus managed to make some progress. The game is Godannar for ps2, a 3-d mecha fighter based on an anime.
It's been ages since I messed with this so I'll jsut post what I can vageuly remember. The basic files were all stored in big AFS files, which you can open with AFSexplorer, google it. Inside those were PAC files (if I remember correctly), which can be taken care of with this tool sanik made for me called
PAC2DIR which will extract the pacs into directories. Often there are pacs within pacs.
I'm going to come abck to this process alter after I make myself pull out the disc and go through it and document it again, but here's the other tools that were also involed, made by a guy calling himself ShinjiIkari,
delzs-godannar and tim2tga. The textures ended up being inside the delzs's and the came out as ps2 tm2's, but were not standard. The delzs's have been seen in other games (he originally made a tool for getting music from wildarms i think it was), and the tool is set up for this specific instance of the format (unless there are others, it's possible). Eventually you'll get tga textures.
Samples:

weird unused? art

human body texture

human face texture
unfortunetly my ultimate goal of getting the models has yet to happen as i know dick about 3d. the plan was to attempt to make the characters from the game playable UT models. if anyone with the skills wants to work with me to give UT players the ability to play as a group of robots, big-tittied women, and big-tittied women in gym uniforms on little robots let me know.
I've also started into getting the art gallery from sonic gems, using some DC format tools I googled up...but only got a layer or two into the files packaging system. if anyone can suggest me some good tools for that let me know.