Following Tim Hall’s suggestion, I will write about my favorite feature: Flashback.
The term “Flashback” covers different technologies. The most useful ones in my opinion are Flashback Query and Flashback Drop, they become very useful in case of human errors. Those errors are much more likely to occur than errors caused by hardware failures. We are all humans and we all make mistakes. Flashback technologies provide easy methods to recover from those errors in contrast to RMAN features for instance.
In the past I already wrote about that, you can the article here: Flashback – Recover without Recovery