Guys, what's a good comeback for "let's just be friends"?

sonic241928
Guys, if a girl you're interested in tells you "you're so nice/sweet/good" or "let's just be friends", or you feel like you're about to be put in the friend zone, what's a good comeback (words or actions) that can make her instantly change her opinion about you (i.e., see you as "not so nice" and more of a challenge)?

Girls, if you ever felt the urge to turn down the advances of a "nice" or "sweet" guy, what could he have done to change your mind right away? What could he have said or done to make you realize, "this guy is more of a challenge than I thought...maybe I don't have him all figured out and he's not that easy to have." Be honest, now ; )

Thanks for your responses.
Updates
+1 y
Are there SPECIFIC things I can do or say to be more of a challenge, BEFORE we become "friends"? I appreciate it if you don't think there are SPECIFIC behaviors, but I do have a reason for asking. Thanks for the responses, I would love to hear more.
Guys, what's a good comeback for "let's just be friends"?
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