Aurification

Whenever a creature deals damage to you, put a gold counter on it.
Each creature with a gold counter on it is a Wall in addition to its other creature types and has defender. (Those creatures can't attack.)
When this enchantment leaves the battlefield, remove all gold counters from all creatures.

Aerial Modification

Enchant creature or Vehicle
As long as enchanted permanent is a Vehicle, it's a creature in addition to its other types.
Enchanted creature gets +2/+2 and has flying.

Acorn Catapult

{1}, {T}: This artifact deals 1 damage to any target. That permanent's controller or that player creates a 1/1 green Squirrel creature token.