Najeela, the Blade-Blossom

Whenever a Warrior attacks, you may have its controller create a 1/1 white Warrior creature token that's tapped and attacking.
{W}{U}{B}{R}{G}: Untap all attacking creatures. They gain trample, lifelink, and haste until end of turn. After this phase, there is an additional combat phase. Activate only during combat.

Seedborn Muse

Untap all permanents you control during each other player's untap step.

Mondrak, Glory Dominus

If one or more tokens would be created under your control, twice that many of those tokens are created instead.
{1}{W/P}{W/P}, Sacrifice two other artifacts and/or creatures: Put an indestructible counter on Mondrak. ({W/P} can be paid with either {W} or 2 life.)

Elesh Norn, Grand Cenobite

Vigilance
Other creatures you control get +2/+2.
Creatures your opponents control get -2/-2.

Primal Vigor

If one or more tokens would be created, twice that many of those tokens are created instead.
If one or more +1/+1 counters would be put on a creature, twice that many +1/+1 counters are put on that creature instead.

Panharmonicon

If an artifact or creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Parallel Lives

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

Mox Amber

{T}: Add one mana of any color among legendary creatures and planeswalkers you control.

Elesh Norn, Mother of Machines

Vigilance
If a permanent entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.
Permanents entering don't cause abilities of permanents your opponents control to trigger.