Llanowar Elves

Wellwisher

{T}: You gain 1 life for each Elf on the battlefield.

Quirion Ranger

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

Timberwatch Elf

{T}: Target creature gets +X/+X until end of turn, where X is the number of Elves on the battlefield.

Umbral Mantle

Equipped creature has "{3}, {Q}: This creature gets +2/+2 until end of turn." ({Q} is the untap symbol.)
Equip {0}

Seeker of Skybreak

Priest of Titania

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

Forest

Elvish Archdruid

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

Elvish Champion

Other Elf creatures get +1/+1 and have forestwalk. (They can't be blocked as long as defending player controls a Forest.)

Fyndhorn Elves

Slate of Ancestry

{4}, {T}, Discard your hand: Draw a card for each creature you control.

Concordant Crossroads

Overrun

Creatures you control get +3/+3 and gain trample until end of turn. (Each of those creatures can deal excess combat damage to the player or planeswalker it's attacking.)