These types of cards allow players to gain perfect information about their opponent's hand, don't cost a card in their hand to play (cause it gets replaced), and helps the player adjust their gameplay accordingly on that turn
How about a tribal cube with archetypes for Goblins, Elves, Soldiers, Merfolk, or even some of the more obscure tribes like Cephalids and Dwarves
It gives those decks a great source of card advantage while also being able to shut down troublesome planeswalkers like Vivien Reid or Ajani, Adversary of Tyrants
10 Goldbug, Humanity's Ally // Goldbug, Scrappy Scout Goldbug, Humanity's Ally does a great job at protecting Human creatures, preventing all combat damage done to them while theyre attacking, allowing you to safely swing all out with an army of humans
Ouroboroid shines in any token or counter-focused strategy
Among all MTG blue spells designed for free interaction, Force of Will stands uniquely alone