It would take a while to compile a list of times in the New Testament when Peter is recorded as speaking. The problem lies in identifying when he was speaking for himself, and when he was speaking as spokesman for the other Apostles. The Bible is not always clear about this, and personal interpretation could come into any answer.
That is demonstrated by the question here, for it is assumed that Peter was speaking on behalf of all the Apostles when he gave that answer to Jesus in Matthew 16:15-16. Not everyone on this site would agree with that interpretation, for many Christians take Peter to be boldly making a personal declaration of faith. They base this on what Jesus then told Peter:
"And Jesus answered and said unto him, 'Blessed art thou, Simon
Barjona: for flesh and blood hath not revealed it unto thee, but my
Father which is in heaven. And I say also unto thee, That thou art
Peter, and upon this rock I will build my church; and the gates of
hell shall not prevail against it. And I will give unto thee the keys
of the kingdom of heaven'..." Matthew 16: 17-19 K.J.V.
Jesus said God had personally revealed that to Peter. Now, if Peter was spokesman on behalf of all the others, why did Jesus address Peter directly with regard to God revealing a truth to him personally, and also regarding the matters following? Surely Jesus would have had to say, "thou art Peter, and also you others will have the keys of the kingdom of heaven" etc.
The matter, however, is complicated by the miracle of Jesus walking on the storm-tossed waters of the Sea of Galilee during the night. This is recorded in chapter 14, and appears to have happened beforehand. All the disciples in the boat declared Jesus to be the Son of God when he and Peter got into the boat, and the storm immediately stopped. When Peter declared Jesus to be the Son of God later, he could have been speaking for the others, for he knew they had all confessed Jesus as the Son of God in the boat, once it stopped rocking.
But given Jesus' very personal remarks to Peter in chapter 16, we cannot assume that. This is what I mean by matters not being clear-cut, when Peter speaks. If there is difficulty sorting that one occasion out (in chapter 16, your example #1), then similar difficulties will be encountered if the Bible does not clearly show that Peter was speaking on behalf of the others. Sometimes he was, sometimes he wasn't, and other times nobody can say with certainty.
Your examples #2, #3, and #4 do state Peter being spokesman. But your example #5, Acts 2:37-38 is not Peter including the apostles in his address. Context shows that all the apostles and the other disciples in the upper room at Pentecost had already received the gift of the Holy Spirit, for they had previously all repented and been baptised, and it was time for that promise of Christ to be fulfilled. After that miracle of grace, the multitude of Jews and proselytes in the city for Pentecost got to hear of the miracle and discovered it to be true. That was when Peter stood up in public and spoke on behalf of all the apostles (vs. 14) to preach the good news of Christ, which required those multitudes to repent and to be baptized in the name of Jesus Christ. The apostles, however, were not being addressed! And the Greek word Peter spoke was 'metanoeo' which cannot be translated as 'do penance', for it means 'to have another mind'. It is not about taking any actions or paying money. Those are just two details, however, which do not detract from Peter speaking to multitudes on behalf of all the apostles. Pardon me if this strikes you as being pedantic, for your main reason for including this as an example stands.
Yet given the difficulties I have mentioned, the answer could only be those times when the record clearly states that Peter was speaking up as spokesman, on behalf of the other Apostles. All personal interpretations of such events would have to be avoided. Therefore, Matthew 16:15-16 is unlikely to be Peter speaking on behalf of all the apostles. If I come across occasions in the New Testament where Peter is clearly stated to be speaking on behalf of the other Apostles (in addition to the examples you have given), I would hope to add to this answer. Or perhaps someone else will beat me to it, in which case, they would deserve the green tick!
