Blockade Runner

{U}: Blockade Runner can't be blocked this turn.

Experiment Kraj

Experiment Kraj has all activated abilities of each other creature with a +1/+1 counter on it.
{T}: Put a +1/+1 counter on target creature.

Aetherling

{U}: Exile Aetherling. Return it to the battlefield under its owner's control at the beginning of the next end step.
{U}: Aetherling can't be blocked this turn.
{1}: Aetherling gets +1/-1 until end of turn.
{1}: Aetherling gets -1/+1 until end of turn.

Advanced Hoverguard

Flying
{U}: Advanced Hoverguard gains shroud until end of turn. (It can't be the target of spells or abilities.)

Agent of Horizons

{2}{U}: Agent of Horizons can't be blocked this turn.

Amaranthine Wall

Defender
{2}: Amaranthine Wall gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Amphin Pathmage

{2}{U}: Target creature can't be blocked this turn.

Argivian Avenger

{1}: Until end of turn, Argivian Avenger gets -1/-1 and gains your choice of flying, vigilance, deathtouch, or haste.

Arcanis the Omnipotent

{T}: Draw three cards.
{2}{U}{U}: Return Arcanis the Omnipotent to its owner's hand.

Beetleform Mage

{G}{U}: Beetleform Mage gets +2/+2 and gains flying until end of turn. Activate only once each turn.