For investors, Giratina V is stellar
M Houndoom EX full art is great, as are both Mewtwo Full arts from Breakthrough
However, Prismatic Ending solves much of this problem, as the card can efficiently answer both creatures and noncreature permanents
Heres an example play, its the same except instead of a Monarch in hand you have a Swap Frog (which is pretty common since you may have sent the Treeborn to grave with it): Summon a Dullahan in the same way as before
It combines the very low voltage resistance (about 40-50 ohms) of a solid core wire with a high level of EMI suppression (equivalent to a 30,000 ohm stock suppression wire)
However, Clefairy is, if anything, an example of how any shadowless Base Set card can sell for surprising amounts, regardless of what's printed on it