Cheapest priced copy (Antiquities): $0.35 at Card Kingdom, near mint, their price list as of .
Phyrexian Gremlins 
Creature — Phyrexian Gremlin · 1/1 · Common · Antiquities · #18
You may choose not to untap this creature during your untap step.
{T}: Tap target artifact. It doesn't untap during its controller's untap step for as long as this creature remains tapped.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
1 printing · $0.35 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Antiquities | 18 | Common | $0.35 | — |
5 rulings from Wizards of the Coast
- 4 October 2004If the Gremlins somehow become an artifact and then tap themselves, they can never be untapped during the untap phase. They must be untapped by an external effect.
- 4 October 2004The target artifact can’t untap if the Gremlins and the artifact are tapped during untap, even if it is your artifact, and you plan on untapping the Gremlins.
- 4 October 2004The effect does not end if the target stops being valid. For example, if it stops being an artifact.
- 4 October 2004Can target a tapped artifact.
- 4 October 2004Only prevents the artifact from untapping during untap step. Ones that untap during upkeep are not inhibited.