In a big-mana deck like Hydra tribal, you can easily set that X to eight or higher, effectively ending the game on the spot as you cast up to eight enemy spells for free
The phenomenon of decks that only have one copy is a bizarre side effect of a world where color is so cheap that you can play this, Wrath of God, Cloudthresher, Jund Charm, and Rhox War Monk without even worrying that this might be pushing it
The five-drop Black one will destroy a dork when it ETBs and equips for free and gives it menace and +1/+{1 size too
We won't rank them here, though, since they arent proper card-draw effects
If you exile a Time Stretch or Primal Surge, good luck to your opponents
Morphing a creature face-up does not cause it to leave or re-enter the battlefield