Forest

Nettle Sentinel

Nettle Sentinel doesn't untap during your untap step.
Whenever you cast a green spell, you may untap Nettle Sentinel.

Harvest Wurm

When Harvest Wurm enters the battlefield, sacrifice it unless you return a basic land card from your graveyard to your hand.

Scythe Tiger

Shroud (This creature can't be the target of spells or abilities.)
When Scythe Tiger enters the battlefield, sacrifice it unless you sacrifice a land.

Borderland Explorer

When Borderland Explorer enters the battlefield, each player may discard a card. Each player who discarded a card this way may search their library for a basic land card, reveal it, put it into their hand, then shuffle.

Rancor

Enchant creature
Enchanted creature gets +2/+0 and has trample.
When Rancor is put into a graveyard from the battlefield, return Rancor to its owner's hand.

Tapping at the Window

Look at the top three cards of your library. You may reveal a creature card from among them and put it into your hand. Put the rest into your graveyard.
Flashback {2}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Rogue Elephant

When Rogue Elephant enters the battlefield, sacrifice it unless you sacrifice a Forest.

Llanowar Stalker

Whenever another creature enters the battlefield under your control, Llanowar Stalker gets +1/+0 until end of turn.

Experiment One

Evolve (Whenever a creature enters the battlefield under your control, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Remove two +1/+1 counters from Experiment One: Regenerate Experiment One. (The next time this creature would be destroyed, instead tap it, remove it from combat, and heal all damage on it.)

Adventurous Impulse

Look at the top three cards of your library. You may reveal a creature or land card from among them and put it into your hand. Put the rest on the bottom of your library in any order.