Vandalblast is a personal favorite of mine, as it can remove a Signal Pest or Expedition Map early, while devastating entire boards late
I still expect it to bottom out at $0.50 before long, but it has some long-term potential due to how unique and flavorful it is
Imperial Bow is the best answer to Evasive characters and can help some of the smaller heroes like Aladdin and Anna trade up into bigger threats, while Thebes offers lore gain for challenging, allowing you to control the board without falling behind on points
5/4 trample for 4 mana is a strong investment already
Impending promoted powerful lines of play, combining enchantment creatures with an intriguing twist on Suspend
Gitaxian Probe The Sac Lands These two cards don't provide quite the same card quality as the spells on the list but they still kind of do and are obviously fantastic cards for there own reasons as well