Might of the Masses

Target creature gets +1/+1 until end of turn for each creature you control.

Symbiosis

Two target creatures each get +2/+2 until end of turn.

Briar Shield

Enchant creature
Enchanted creature gets +1/+1.
Sacrifice Briar Shield: Enchanted creature gets +3/+3 until end of turn.

River Boa

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
{G}: Regenerate River Boa.

Forest

Giant Growth

Target creature gets +3/+3 until end of turn.

Seal of Strength

Sacrifice Seal of Strength: Target creature gets +3/+3 until end of turn.

Llanowar Elves

Elvish Mystic

Rogue Elephant

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

For the Family

Target creature gets +2/+2 until end of turn. If you control four or more creatures, that creature gets +4/+4 until end of turn instead.

Pouncing Jaguar

Echo {G} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)

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.