Oh boy, I don't know, I'd have to just say my collection as a whole which has taken many years to get to the point I'm at now with it as I'm only about 20 items away from having an original (CD/vinyl) of (at least) one copy of every studio & live song that has ever been released legally that has at least one member (of all the 16 Mac members) on the recording (as far as I know anyways) in some form (though I must admit, I'm not really into the "remixes" or other artists "covering" songs written by a FM member (unless one of the FM members plays/sings on it of course). For my collection, at least one of the 16 gotta be on the recording, whether they are playing something or backing vocals or whatever) though I can certainly understand why many of you do like the "remixes" & "covers", there's so many fascinating things to come across whist FM collecting!
I've got a couple limited edition things where there were only a couple hundred pressed or whatever but it would take longer to explain their relevance to my collection than it's worth and it'd probably send many of you to sleep as many of those relate mainly to the more, how shall we say, "obscure" members of FM (Brunning, Mason, Walker, Weston, etc.).
Good question Adam! I'm looking forward to seeing what others have to say on this as well!
John