This will usually be your vanilla Red-Eyes Black Dragon
This means, that the cost of activating the ability (1 colorless energy) is meaningless if the rival has an ability that costs 3 energy (from any type), as Ditto won't be able to use the attack, and will waste its turn doing basically nothing
Staples Kiki-Jiki, Mirror-Breaker Recoup This ones pretty contextual, but its hard to imagine a deck that cant take significant advantage of it
SR Super Rare UR Ultra Rare SE Secret Rare UL Ultimate Rare PS Platinum Secret Rare CR COLLECTOR'S RARE QCSE Quarter Century Secret Rare Dragonmaid Hospitality X SPELL Special Summon 1 "Dragonmaid" monster from your hand or GY in Defense Position, then, you can send 1 "Dragonmaid" monster with the same Attribute, but a different Level, from your Deck to the GY
They always seem to have the right blue draw cards mtg or counterspell ready to foil opponents' plans