It's still unclear if there are more out there, but the likelihood steadily decreases as the years go by. The Pikachu Illustrator currently under the hammer has a top bid of $220,000 at the time of writing
Countermagic : Mystic Snake, Frilled Mystic, Draining Whelk Reanimation : Karmic Guide, Phyrexian Delver, Extraction Specialist Milling : Manic Scribe, Thieves' Guild Enforcer, Sage's Row Denizen Self-Milling : Stitcher's Supplier, Satyr Wayfinder, Balustrade Spy Discard : Burglar Rat, Mesmeric Fiend, Sin Collector Goading : Insufferable Balladeer, Jeering Homunculus, Vengeful Ancestor "Gain Control" effects : Hostage Taker, Agent of Treachery, Gonti, Lord of Luxury Clones : virtually all of them, though a few are decently pricey
The puzzle is: when is it best to crack your clues and what will you be able to pay for after you spend
If it is not, it can be used for any Extra Deck or Tribute Summon