Activated Abilities

[Bookmeister]

Can you use activated abilities of creatures the turn they ETB if they do not tap the creature?

[Keyeto]

As long as you have what is required to activate the ability, absolutely.

RESOLVED

[Agarrita80]

But if activation cost asks you to tap creature to activate, Then you cannot cast it on the turn that it comes into play unless it has haste.

[The1337Magician]

Yes. Correct.

[Double-O-Scotch]

Orrrr if the activation cost is "tap a creature you control : get such and such effect"
You could tap a creature with summoning sickness to pay this cost, correct?

[MementoMori]

Yes. If a creature with summoning sickness has an ability with the {T} symbol, you can't use it. Everything else is fair game.