Once you've announced that you're casting a spell, players can't take any actions until you've finished doing so
Goblin Test Pilot: When Goblin Test Pilot deals damage to a creature or player, flip a coin
That's why it almost cracked my top five
This mono-blue planeswalker is all about getting the most out of your artifacts, with his first ability letting you untap up to two artifacts so you can keep the value going
While red has a lot of powerful Creatures that you could theoretically search for under these conditions, the mana cost, and Imperial Recruiters weak stats, leave it sorely lacking compared to the tutoring competition
It however is still considered to be in exile and not on the battlefield or your hand, meaning that there are much fewer ways for your opponent to be able to get rid of it before you can cast it