This definitive, end of story proof can be used in debates with Sunni brothers and sisters,
Chapter: Virtues of companions: http://www.sahihmuslim.com/sps/smm/sahihmuslim.cfm?scn=dspchapters&BookID=31
Subchapter: THE MERITS OF 'ALI B. ABI TALIB (ALLAAH BE PLEASED WITH HIM):http://www.sahihmuslim.com/sps/smm/sahihmuslim.cfm?scn=dspchaptersfull&BookID=31&ChapterID=1002
Hadith #: No. 5920: http://www.sahihmuslim.com/sps/smm/
Yazid b. Hayyan reported, I went along with Husain b. Sabra and 'Umar b. Muslim to Zaid b. Arqam and, as we sat by his side, Husain said to him: Zaid. you have been able to acquire a great virtue that you saw Allaah's Messenger (sallAllaahu alayhi wa sallam) listened to his talk, fought by his side in (different) battles, offered prayer behind me. Zaid, you have in fact earned a great virtue. Zaid, narrate to us what you heard from Allaah's Messenger (sallAllaahu alayhi wa sallam). He said: I have grown old and have almost spent my age and I have forgotten some of the things which I remembered in connection with Allaah's Messenger (sallAllaahu alayhi wa sallam), so accept whatever I narrate to you, and which I do not narrate do not compel me to do that. He then said: One day Allaah's Messenger (sallAllaahu alayhi wa sallam) stood up to deliver sermon at a watering place known as khumm situated between Mecca and Medina. He praised Allaah, extolled Him and delivered the sermon and. exhorted (us) and said: Now to our purpose. O people, I am a human being. I am about to receive a messenger (the angel of death) from my Lord and I, in response to Allaah's call, (would bid good-bye to you), but I am leaving among you two weighty things: the one being the Book of Allaah in which there is right guidance and light, so hold fast to the Book of Allaah and adhere to it. He exhorted (us) (to hold fast) to the Book of Allaah and then said: The second are the members of my household I remind you (of your duties) to the members of my family. He (Husain) said to Zaid: Who are the members of his household? Aren't his wives the members of his family? Thereupon he said: His wives are the members of his family (but here) the members of his family are those for whom acceptance of Zakat is forbidden. And he said: Who are they? Thereupon he said: 'Ali and the offspring of 'Ali, 'Aqil and the offspring of 'Aqil and the offspring of Ja'far and the offspring of 'Abbas. Husain said: These are those for whom the acceptance of Zakat is forbidden. Zaid said: Yes.
Shia: surely a great messenger of Allah would have left behind something to guide us..
Sunni: he did, Quran and Sunnah
Shia: I swear by the holy kaba'a that I will become Sunni if you show me one hadith in one of the Sahi's that says Quran and Sunnah I will become Sunni.
Sunni: What is the hadith then?
Shia: Quran and ahl ul bayt.
Sunni: Prove it...
You know what to do....