Cheapest priced copy (Shadowmoor): $0.35 at Card Kingdom, near mint, their price list as of .
Safehold Sentry 
Creature — Elf Warrior · 2/2 · Common · Shadowmoor · #22
{2}{W}, {Q}: This creature gets +0/+2 until end of turn. ({Q} is the untap symbol.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Shadowmoor | 22 | Common | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 1 May 2008If the permanent is already untapped, you can't activate its {Q} ability. That's because you can't pay the "Untap this permanent" cost.
- 1 May 2008If a creature with an {Q} ability hasn't been under your control since your most recent turn began, you can't activate that ability, unless the creature has haste.
- 1 May 2008When you activate an {Q} ability, you untap the creature with that ability as a cost. The untap can't be responded to. (The actual ability can be responded to, of course.)