Safehold Sentry
Creature — Elf Warrior
, 
: This creature gets +0/+2 until end of turn. ( is the untap symbol.)
"These bracers were worn by my father and by his mother before him. Boggart fangs have shattered on them. Cinder flames have withered at their touch. While I wear them, the safehold will not fall."
William O'Connor
Shadowmoor (SHM)
• #22Rulings
If the permanent is already untapped, you can't activate its {Q} ability. That's because you can't pay the "Untap this permanent" cost.
(wotc • 2008-05-01)
If 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.
(wotc • 2008-05-01)
When 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.)
(wotc • 2008-05-01)
Rulings
If the permanent is already untapped, you can't activate its {Q} ability. That's because you can't pay the "Untap this permanent" cost.
(wotc • 2008-05-01)
If 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.
(wotc • 2008-05-01)
When 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.)
(wotc • 2008-05-01)