You're right that the recombobulator could be a sleeper hit here, which was my intention obviously. And you're right that there isn't really an 8 drop to use the effect on unless Sneed's is silenced.
I would argue that the best targets to use Recombobulator on would be Ancient of Lore & Cenarius.
7 drops are one of the rarest mana costed cards and most of the new 7 mana drops are a much larger body than Ancient of Lore. So once you use the AoL battlecry you could easily combo with recombobulator on 9 mana to try for a bigger body.
7 Drops:
Archmage Antonidas
Barron Geddon
Prophet Velen
Ancient of Lore
Ancient of War
Ravenholdt Assassin
Core Hound
Guardian of Kings
Stormwind Champion
War Golem
Dr. Boom
Flame Leviathan
Gahz'rilla
Malorne
Neptulon
Troggzor the Erthinator
9 drops are even rarer, and almost all of them are much better than Cenarius as a body on board. Only Lord Jaraxxus would probably be considered as worse.
After using Cenarius for his battlecry (probably for the taunts), if he sticks around a turn, or if you have innervate, you could recombob for something else:
9 Drops:
Mal Ghanis
Mekgineer Thermaplugg
Alexstraesza
Cenarius
King Krush
Lord Jaraxxus
Malygos
Nozdormu
Onyxia
Ysera
The Dream: Mal Ghanis / Krush / Ysera