Wow. Lots of replies. Sorry I couldn't comment earlier, 60 hour work week, you know how it goes.
Yes, I meant most powerful, but let me caveat that further. Power can be measured in two ways.
A) Most powerful for a cleric devoid of group considerations, or
B) most powerful for a cleric set in the standard four member party. With these criteria, my questions stands altered as so.
And yes, my faux pas, Slime definitely rocks for (A), but probably not (B) as a priest of Ghanadaur's (correct spelling ?) moral bent is probably not best suited for a party.
Luck seems alright in my book. Everyone could use a reroll now and then.
The Family domain power, while once a day, is very strong and is invoked as a free action.
I may have overlooked Renewal.
Good comments Celebrim.
Planning gives you (imo) one of the better metamagic feats in the game and the Clairvoyance/Clairaudience spell at 3rd level, perhaps the optimal information gathering low level spell.