"The anime are restless!" Love that line. When I'm playing alone with my headphones and I hear it I go:
ME: Hey, guess what!
EVERYONE ELSE IN THE ROOM: What?
ME: The anime are restless.
EVERYONE ELSE IN THE ROOM: * rolls eyes *
Other awesome lines:
"Theeeey don't look friendly."
"I come to DESTROY!"
"This is how space junk is born!"
"The Unity has fallen silent on one of our planets!"
I give Sins the 2nd best voice acting of any strategy game I've played (second only to the incredibly immersive, gloriously stereotypical, totally irreverent, and often hilarious Command and Conquer: Generals).