What are some lesser known facts about Christianity?

I tend to be interested in some of the Gnostic groups and sects of early Christianity; for many people, all knowledge of these groups comes from something like The Da Vinci Code, which is a nice way in which to grow interested but which certainly exaggerates, cherry-picks, and even makes up material at some points. It's Gnostic revival, but Catharism is also very interesting.

I am often amazed that apparently the fact that Jesus was Jewish is widely unknown to many.

Interesting. I suppose that the fact that Buddha was Hindu is widely unknown to many too.

a. you can indeed cherry pick from the bible whatever seems to work in your chosen lifestyle and still maintain an air of self-righteousness only found at swap meets and carnival attractions.

The word "cross" is never explicitly mentioned in the original untranslated scriptures

There's certainly a lot of heat and noise created by Christians around abortion, which as already noted is not mentioned in scripture. Divorce on the other hand, which is specifically mentioned, several times and in negative terms -  including by JC himself - seems to bother hardly anyone.

Is it? What else do they think he was? What else could he have been? 

Nor was the penitent thief ever described in the bible as having ever actually “repented”. In the exchange, he merely acknowledges that he committed crimes, states that he deserves the punishment, and asks for forgiveness and for Jesus to remember him. Jesus then promises that he will be with him in Paradise. But at no point did the thief ever express “regret” or “remorse” for his actions. Nor did this thief ever have the opportunity to become baptized (washing away his sins/being born again), casting doubt on the idea that he ever actually received the Holy Spirit. He merely confesses his sins on his death bed, but “confession” alone is not necessarily “repentance”. Nevertheless, Catholic tradition has venerated the thief, and the traditional Christian assumption is that he was forgiven and went to paradise based on Jesus’s promise. 

The “Penitent Thief” brings up a good point about the Bible in general and the Gospels in particular: when Bible stories appear in different places, there are often significant differences between the versions.

The Penitent Thief only appears in one of the four Gospels. Luke 23:39-43 tells the story that is being discussed on this thread. Matthew 27:38 simply says that two robbers were crucified with him, one on his right and one on his left. Matthew adds that the robbers were mocked by passers-by the same as Jesus. Mark 15:27 says the same thing (most scholars believe that Matthew used Mark as a source), but leaves out the comment about the robbers also being mocked. In Mark only Jesus gets the crowd’s rebuke. John 19:18 also just mentions the robbers in passing, but later in the chapter says that they had their legs broken by the Romans (to induce shock and then death), but that Jesus was already dead so did not have his legs broken. This detail is found only in John.

The takeaway then is that the author we call “Luke” created the story to make a theological point. Whatever historical (as opposed to theological) truth is contained in the Passion narrative, it is probably that the others executed with Jesus played no other part in the event except to be there and die. Another little known aspect is that although the Gospels may contain history, they are documents of faith, not biography. There was no concept of writing history as we think of it. The stories within them demonstrate to their first readers what to believe and how to act in their own lives.