Eddard

In this chapter Ned confronts Cersie about knowing that Joffery and her other kids are not fathered by King Robert and in fact are her brother Jamie's kids. During the conversation Cersie admits to Ned that Jamie and her had tried to kill Bran because he saw her and Jamie. Ned takes the news about Bran pretty well and still urges Cersie to take her kids and flee Kings Landing. Cersie told Ned she wouldn't do no such thing like flee.
I chose this chapter because Ned revealing that he knew this confidential information to Cersie of all people is huge. Foreshadowing if Cersie isn't willing to flee with her children what other options does she really have I highly doubt that she neither Jamie will let anyone harm their children, so something big has to be coming. This chapter sets in motion huge plays for the throne in upcoming chapters.