this game is quite annoyin' when tryin' to acheive sumthin', but...here goes.
1) you need to be a "a" then a "s" rank to unlock greed, izumi, pride and wrath. (in that order) to get these rankings you need to play arcade mode then, save the team you've chosen in arcade mode and load up that team up every time you play. after playin' w/ that team numerous times, your rank will rise. (i've noticed that when playin' arcade mode, when new items start to appear, your rank will rise shortly afterwards.) items for characters: greed=ultimate shield (a rank required) izumi=her isignia (same kind ed and al have) (a rank required) pride=eyepatch (s rank) wrath=homonculus insignia (gluttony will have this one.) (s rank)
after collectin' these items, just transmute them by themselves. ta-da!!!
(didn't feel like mentionin' how to unlock scar and the rest, since all you gotta do is beat story mode.)