Titanoth Rex

Trample
Cycling {1}{G} ({1}{G}, Discard this card: Draw a card.)
When you cycle Titanoth Rex, put a trample counter on target creature you control.

Beastmaster Ascension

Whenever a creature you control attacks, you may put a quest counter on Beastmaster Ascension.
As long as Beastmaster Ascension has seven or more quest counters on it, creatures you control get +5/+5.

Fyndhorn Elves

Dragon Throne of Tarkir

Equipped creature has defender and "{2}, {T}: Other creatures you control gain trample and get +X/+X until end of turn, where X is this creature's power."
Equip {3}

Surrak, the Hunt Caller

At the beginning of combat on your turn, if creatures you control have total power 8 or greater, target creature you control gains haste until end of turn. (It can attack and {T} no matter when it came under your control.)

Gnoll Hunter

Pack tactics — Whenever Gnoll Hunter attacks, if you attacked with creatures with total power 6 or greater this combat, put a +1/+1 counter on Gnoll Hunter.

Ghalta, Primal Hunger

This spell costs {X} less to cast, where X is the total power of creatures you control.
Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)

Sinuous Predator

Sinuous Predator can't be blocked by more than one creature.

Kessig Prowler

Kessig Prowler // Sinuous Predator

Circle of Elders

Vigilance
Formidable — {T}: Add {C}{C}{C}. Activate only if creatures you control have total power 8 or greater.

Nature's Way

Target creature you control gains vigilance and trample until end of turn. It deals damage equal to its power to target creature you don't control.

Pulse of Murasa

Return target creature or land card from a graveyard to its owner's hand. You gain 6 life.

Rural Recruit

Training (Whenever this creature attacks with another creature with greater power, put a +1/+1 counter on this creature.)
When Rural Recruit enters, create a 3/1 green Boar creature token.

Giant Growth

Target creature gets +3/+3 until end of turn.

Overwhelming Stampede

Until end of turn, creatures you control gain trample and get +X/+X, where X is the greatest power among creatures you control.