Lotus Petal

{T}, Sacrifice Lotus Petal: Add one mana of any color.

Crookshank Kobolds

Mob Mentality

Enchant creature
Enchanted creature has trample.
Whenever all non-Wall creatures you control attack, enchanted creature gets +X/+0 until end of turn, where X is the number of attacking creatures.

Simian Spirit Guide

Exile Simian Spirit Guide from your hand: Add {R}.

Reckless Charge

Target creature gets +3/+0 and gains haste until end of turn.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Forest

Atog

Sacrifice an artifact: Atog gets +2/+2 until end of turn.

Wild Cantor

({R/G} can be paid with either {R} or {G}.)
Sacrifice Wild Cantor: Add one mana of any color.

Memnite

Phyrexian Walker

Shield Sphere

Defender
Whenever Shield Sphere blocks, put a -0/-1 counter on it.

Glimpse of Nature

Whenever you cast a creature spell this turn, draw a card.

Serum Powder

{T}: Add {C}.
Any time you could mulligan and Serum Powder is in your hand, you may exile all the cards from your hand, then draw that many cards. (You can do this in addition to taking mulligans.)

Street Wraith

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Cycling—Pay 2 life. (Pay 2 life, Discard this card: Draw a card.)

Stonecoil Serpent

Reach, trample, protection from multicolored
Stonecoil Serpent enters with X +1/+1 counters on it.