I think it's the gloval.sav, but I'm not too sure...
Just to be sure it is better to backup all the Tsukihime folder ( the virtual store Tsukihime folder, not the one that the game is installed. That is, supposing you're running the game in Windows)
"Let Chaos consume your soul, and you won't be neither good nor evil, neither light nor darkness. You will be hollow, will be future, will be freedom." -Chaos Chaud
"You defeat him" -GARcher
"Drown in your ideals and die" -GARcher
"My spine hurts. My body is cold. My fingers are frozen. Yet, my brain burns with fire."- T. Shiki