I would have to say my favorite quotes are all Eastwood, because, I mean, c'mon, it's The Man With No Name. I need not elaborate.
Anyway, here they are:
"Get three coffins ready..."
"If you hold your breath I feel a man like you could manage it."
"You have to die."
In response to Cavanagh at the saloon in FAFDM asking what the bet was: "Your life."
"You shoot to kill, you better hit the heart. Your own words, Ramone."