In my opinion, the penitent thief is the greatest example of salvation. At first, he sinned. We know he sinned, he was human, and of course when we first meet him in scripture, he was being punished for his own sin. Furthermore, it appears that he began by mocking Jesus. Matthew 27:44 tells us the robbers (plural) who were crucified with Him mocked Him, which strongly indicates the penitent thief initially joined in with the mockery. Regardless of whether or not the penitent thief initially mocked Jesus, we know He was still a sinner.
But he did not stay a sinner. At some point during the crucifixion, he acknowledged "And we indeed justly, for we receive the due reward of our deeds(...)" (Luke 23:41a). This is the first step to salvation: Confessing the very need of a saviour. "We receive the due reward of our deeds". This thief knew he deserved his condemnation, and confessed it aloud.
And then He turns to Jesus and confesses "...but this Man has done nothing wrong." Here we have the beginnings of recognising who Jesus is. Jesus, though knowing no sin, nevertheless suffered for sin. And so the thief continued, "Lord, remember me when you come into your Kingdom." And there we have it. The confession of Christ as Lord, and the belief that He would rise in glory. As Romans 10:9 tells us, if you confess with your mouth the Lord Jesus, and believe in your heart that God raised Him from the dead, you will be saved.
Thus, the penitent thief is the greatest example of salvation. This actually settles a number of disputes in Christianity. "What must I do to be saved"? Nothing you couldn't do with your hands and feet nailed down. Is baptism necessary for salvation? No, the thief was saved, yet not baptised. What about the Eucharist? No, the thief doesn't seem to have had the luxury of bread or wine. Confess, repent, believe, receive.
Some object to the use of the thief on the cross in such a manner. It is claimed that he was actually under old covenant rules. There are, however, two problems with this. First, he does not appear to have fulfilled the Old Testament requirements either (unless we go to the right depth and recognise that faith was also the requirement in the Old Testament). The second, however, is that Hebrews 9:15-17 tells us that the death of Christ ended the Old Covenant, and brought in the New. Jesus died first, whereas the Romans had to break the legs of both thieves to accelerate their deaths (John 19:31-33). Thus, the thief did, in fact, die in the new covenant, not the old.
As Christians, we are all saved in the manner of the penitent thief. We began as sinners, even to the point of explicitly rebelling against Christ. And yet, we recognised that our due reward is death. Yet, though He knew no sin, He became sin for us, that we might become His righteousness. Therefore, we confess Him as Lord, and believing He rose from the dead, ask Him to likewise raise us. Yet, unlike the penitent thief, most of us have the luxury of longevity. We are not nailed down, but standing up. Therefore, it is our privilege to be baptised, and take the Gospel to all nations, baptising them also and teaching them to obey all that Christ commanded. Praise God for the penitent thief, for we are all like him.