"Why should I? What's in it for me?" 
"Your bargaining posture is highly dubious, but very well. I will provide you with a new body and new troops to command." 
"And?" 
"And nothing! You belong to me now." 
"I belong to nobody!" 
"Perhaps I misjudged you. Proceed, on your way to Oblivion." 
"Argh! No! No, I accept your terms! *more screaming*" 
"Excellent." 
  
Yeah, that almost works for Mass Effect.