Viridian Lorebearers

{3}{G}, {T}: Target creature gets +X/+X until end of turn, where X is the number of artifacts your opponents control.

Planeswalker's Favor

{3}{G}: Target opponent reveals a card at random from their hand. Target creature gets +X/+X until end of turn, where X is the revealed card's mana value.

Thriss, Nantuko Primus

{G}, {T}: Target creature gets +5/+5 until end of turn.

Nantuko Mentor

{2}{G}, {T}: Target creature gets +X/+X until end of turn, where X is that creature's power.

Meandering Towershell

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Meandering Towershell attacks, exile it. Return it to the battlefield under your control tapped and attacking at the beginning of the declare attackers step on your next turn.

Power Matrix

{T}: Target creature gets +1/+1 and gains flying, first strike, and trample until end of turn.

Ogre Battledriver

Whenever another creature you control enters, that creature gets +2/+0 and gains haste until end of turn. (It can attack and {T} this turn.)

Ambuscade Shaman

Whenever Ambuscade Shaman or another creature you control enters, that creature gets +2/+2 until end of turn.
Dash {3}{B} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)

Berserkers' Onslaught

Attacking creatures you control have double strike.

Primal Forcemage

Whenever another creature you control enters, that creature gets +3/+3 until end of turn.