Fire of Unknown Origin is my personal favorite as far as an "overall" BOC studio album goes.
Club Ninja would come in a close second for me. Dancin' in the Ruins and Perfect Water are a couple of their more underrated songs IMO.
Agents of Fortune is of course a classic album due to the inclusion of (Don't Fear) The Reaper, but as for the other songs on the LP, they've never been up there at the top to my ears.
"Through unlit corridors of purest oblivion.
Submerged in a sea of darkness without end.
To feel nothing...hear nothing...for a thousand eternities." - Evoken - Quietus