Chaotic Goo Chaotic Goo alone is only okay, but it works much better in decks built around +1/+1 counters
Starting with an eight-card hand thanks to a companion while your opponent starts with seven is actually pretty similar to the mulligan situation above
Zahur, Glorys Past is another cheap card that starts engines
The Obscura, masters of secrets and manipulation, got connive
As a Torpor Orb on legs, with flash to boot, you can bring out a nasty shock to someone who is relying on cards such as Mulldrifter, Stoneforge Mystic, or Rune-Scarred Demon
Take Volo, Guide to Monsters, for example: if you were to cast a creature spell that has no creature types while hes on the field, youre guaranteed to get a copy of that spell