His Oath, the Oath of Ajani, is a legendary enchantment with a casting cost of one green and one white mana
That way beasts can get better without busting Standard
The rule at the time was you should play your cards as written, and as written, you could discard or mill a Rukh Egg and still get the 4/4 token, which led to the card being banned before Wizards eventually updated the wording
You could do something as simple as adding an extra -1/-1 counter to an enemy creature, or you could really ruin someone's day by doling out poison counters at an alarming rate
The Ozolith - So your shield counters don't go to waste Tromell, Seymour's Butler He turns ETB engines into a festival of proliferate
Stern Proctor is another great choice, and its very rarely without a few good targets