Undercosted: Blue (Monastery Siege-paper $2.49 Jan 20 15) at 3, Dragons can slow opponent a lot.
Normal cost (at 4): Green (Frontier Siege-paper $1.29 Jan 20 15) at 4, Khans, mana source.
At 3 cost, Green (Yasova-paper $1.64 Jan 20 15) has a repeatable Act of Treason.
Black (Tasigur-paper $4.87 Jan 20 15) is over-costed but with Delve can be a one-drop... can be broken. You can filter your graveyard to limit opponent's choice for the hybrid ability.
one-drop Green can be abused with mana dorks, best card in the set.
[Warden of the First Tree-paper $8.00 Jan 20 15]
two-drop White can be abused for free spells, yet at a heavy cost, and you still need to pay the casting cost of the repeatable spell.
[Soulfire Grand Master-paper $19.02 Jan 20 15]
four-drop Black can make a mean Deathtouch deck in Standard, but a 5 mana activation cost looks difficult to pull off in any other format.
[Brutal Hordechief-paper $8.49 Jan 20 15]
four-drop Red has card draw in the Ferocius ability but at 4 mana a pop... good in Standard for sure.
[Shaman of the Great Hunt-paper $9.09 Jan 20 15]
five-drop Blue is actually good because of the tapping ability when it attacks ('all creatures' is GREAT).
[Torrent Elemental-paper $5.50 Jan 20 15]
Dromoka [paper $1.49 Jan 20 15] and Kolaghan [paper $2.03 Jan 20 15] are five drops, and that makes them worth a try. The other three are over-costed Johnny rares.