One of my favorites is from Ganondorf:
The history of light and shadow will be written in blood!
Then, I'd say these probably are my favorites:
The right thing... what is it? I wonder, if you do the right thing, does it really make everyone happy?
Your true face... What kind of... face is it? I wonder... The face under the mask... Is that... your true face?
Can I ask... a question? Your friends... What kind of... people are they? I wonder... Do these people... think of you... as a friend?
Can I ask... a question? What makes you happy? I wonder... what makes you happy... does it make... others happy, too?
Also, this one from the Happy Mask Salesman:
Whenever there is a meeting, a parting shall follow. But that parting needs not last forever. Whether a parting be forever or merely for a short while... that is up to you.