Phyrexian Gremlins

You may choose not to untap Phyrexian Gremlins during your untap step.
{T}: Tap target artifact. It doesn't untap during its controller's untap step for as long as Phyrexian Gremlins remains tapped.

Damping Field

Players can't untap more than one artifact during their untap steps.

Venarian Gold

Enchant creature
When Venarian Gold enters, tap enchanted creature and put X sleep counters on it.
Enchanted creature doesn't untap during its controller's untap step if it has a sleep counter on it.
At the beginning of the upkeep of enchanted creature's controller, remove a sleep counter from that creature.

Mystic Restraints

Flash
Enchant creature
When Mystic Restraints enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Telekinesis

Tap target creature. Prevent all combat damage that would be dealt by that creature this turn. It doesn't untap during its controller's next two untap steps.