Initiate's Companion

Whenever Initiate's Companion deals combat damage to a player, untap target creature or land.

Civic Gardener

Whenever Civic Gardener attacks, untap target creature or land.

Gift of Growth

Kicker {2} (You may pay an additional {2} as you cast this spell.)
Untap target creature. It gets +2/+2 until end of turn. If this spell was kicked, that creature gets +4/+4 until end of turn instead.

Puppet Strings

{2}, {T}: You may tap or untap target creature.

Seeker of Skybreak

Fyndhorn Brownie

Steady Aim

Untap target creature. It gets +1/+4 and gains reach until end of turn.

Elmar, Ulvenwald Informant

Haste
Whenever you cast your second spell each turn, untap target creature, then investigate. (Create a colorless Clue artifact token with "{2}, Sacrifice this artifact: Draw a card.")
Friends forever (You can have two commanders if both have friends forever.)

Scryb Ranger

Flash
Flying, protection from blue
Return a Forest you control to its owner's hand: Untap target creature. Activate only once each turn.

Jandor's Saddlebags

Magewright's Stone

{1}, {T}: Untap target creature that has an activated ability with {T} in its cost.

Staff of Domination

{1}: Untap Staff of Domination.
{2}, {T}: You gain 1 life.
{3}, {T}: Untap target creature.
{4}, {T}: Tap target creature.
{5}, {T}: Draw a card.

Ornamental Courage

Untap target creature. It gets +1/+3 until end of turn.

Jegantha, the Wellspring

Companion — No card in your starting deck has more than one of the same mana symbol in its mana cost. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
{T}: Add {W}{U}{B}{R}{G}. This mana can't be spent to pay generic mana costs.

Aim High

Untap target creature. It gets +2/+2 and gains reach until end of turn. (It can block creatures with flying.)

Spidery Grasp

Untap target creature. It gets +2/+4 and gains reach until end of turn. (It can block creatures with flying.)

Seize the Day

Untap target creature. After this main phase, there is an additional combat phase followed by an additional main phase.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Thousand-Year Elixir

You may activate abilities of creatures you control as though those creatures had haste.
{1}, {T}: Untap target creature.