Quirion Ranger

Return a Forest you control to its owner's hand: Untap target creature. Activate only once each turn.

Priest of Titania

{T}: Add {G} for each Elf on the battlefield.

Wirewood Herald

When Wirewood Herald dies, you may search your library for an Elf card, reveal that card, put it into your hand, then shuffle.

Stroke of Genius

Elvish Archdruid

Other Elf creatures you control get +1/+1.
{T}: Add {G} for each Elf you control.

Llanowar Elves

Island

Fireball

This spell costs {1} more to cast for each target beyond the first.
Fireball deals X damage divided evenly, rounded down, among any number of targets.

Nullmage Shepherd

Tap four untapped creatures you control: Destroy target artifact or enchantment.

Fyndhorn Elves

Eladamri, Lord of Leaves

Other Elf creatures have forestwalk. (They can't be blocked as long as defending player controls a Forest.)
Other Elves have shroud. (They can't be the targets of spells or abilities.)

Rofellos, Llanowar Emissary

{T}: Add {G} for each Forest you control.

Forest

Lys Alana Huntmaster

Whenever you cast an Elf spell, you may create a 1/1 green Elf Warrior creature token.

Wood Elves

When Wood Elves enters, search your library for a Forest card, put that card onto the battlefield, then shuffle.

Mountain

Nomadic Elf

Leaf-Crowned Visionary

Other Elves you control get +1/+1.
Whenever you cast an Elf spell, you may pay {G}. If you do, draw a card.