Chakram Retriever

Partner with Chakram Slinger (When this creature enters, target player may put Chakram Slinger into their hand from their library, then shuffle.)
Whenever you cast a spell during your turn, untap target creature.

Magewright's Stone

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

Maze of Ith

{T}: Untap target attacking creature. Prevent all combat damage that would be dealt to and dealt by that creature this turn.

Ghostly Touch

Enchant creature
Enchanted creature has "Whenever this creature attacks, you may tap or untap target permanent."

Voyaging Satyr

Minamo, School at Water's Edge

{T}: Add {U}.
{U}, {T}: Untap target legendary permanent.

Deserted Temple

{T}: Add {C}.
{1}, {T}: Untap target land.

Thousand-Year Elixir

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

Puppet Strings

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

Captain of the Mists

Whenever another Human you control enters, untap this creature.
{1}{U}, {T}: You may tap or untap target permanent.

Arixmethes, Slumbering Isle

Arixmethes enters tapped with five slumber counters on it.
As long as Arixmethes has a slumber counter on it, it's a land. (It's not a creature.)
Whenever you cast a spell, you may remove a slumber counter from Arixmethes.
{T}: Add {G}{U}.

Kiora, Behemoth Beckoner

Whenever a creature you control with power 4 or greater enters, draw a card.
−1: Untap target permanent.

Blossom Dryad

Stone-Seeder Hierophant

Landfall — Whenever a land you control enters, untap this creature.
{T}: Untap target land.

Ley Druid

Mirran Spy

Flying
Whenever you cast an artifact spell, you may untap target creature.

Arbor Elf

Hope Tender

{1}, {T}: Untap target land.
{1}, {T}, Exert this creature: Untap two target lands. (An exerted creature won't untap during your next untap step.)

Aphetto Alchemist

{T}: Untap target artifact or creature.
Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)