Forest

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.)

Nykthos, Shrine to Nyx

{T}: Add {C}.
{2}, {T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Imperious Perfect

Other Elves you control get +1/+1.
{G}, {T}: Create a 1/1 green Elf Warrior creature token.

Ezuri, Renegade Leader

{G}: Regenerate another target Elf.
{2}{G}{G}{G}: Elf creatures you control get +3/+3 and gain trample until end of turn.

Priest of Titania

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

Parallel Lives

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

Llanowar Elves

Dwynen, Gilt-Leaf Daen

Reach
Other Elf creatures you control get +1/+1.
Whenever Dwynen, Gilt-Leaf Daen attacks, you gain 1 life for each attacking Elf you control.

Dwynen's Elite

When Dwynen's Elite enters, if you control another Elf, create a 1/1 green Elf Warrior creature token.

Elvish Archdruid

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