Llanowar Elves

Wildborn Preserver

Flash
Reach
Whenever another non-Human creature you control enters, you may pay {X}. When you do, put X +1/+1 counters on Wildborn Preserver.

End-Raze Forerunners

Vigilance, trample, haste
When End-Raze Forerunners enters, other creatures you control get +2/+2 and gain vigilance and trample until end of turn.

Elvish Warmaster

Whenever one or more other Elves you control enter, create a 1/1 green Elf Warrior creature token. This ability triggers only once each turn.
{5}{G}{G}: Elves you control get +2/+2 and gain deathtouch until end of turn.

Forest

Dwynen's Elite

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

Fierce Empath

When Fierce Empath enters, you may search your library for a creature card with mana value 6 or greater, reveal it, put it into your hand, then shuffle.

Ghalta, Primal Hunger

This spell costs {X} less to cast, where X is the total power of creatures you control.
Trample