Just about every rare item can be dropped by just about anything. There are a few exceptions... Soul Eater, for one, takes a long and arduous quest... I don't know about the frying pan (How do you get it??
), certain monsters drop certain body parts which can be changed into weapons... AFAIK al rappies drop mag cells... etc... but rares like Photon Claw, Fake Agitos, Varista's, etc... can be found just about anywhere on its appropriate level (ie Varistas Hard levels and up, Clubs of Laconium on V.Hard Mines and Ruins) etc... of course they can throw you off as well, such as Delsabers dropping Sinow Beat's Arms (go fig). All it is, is a matter of luck (the real thing, not the stat).