So the biggest problem I see with Third Person Omniscient is that the Narrator is all knowing and no facts of the story are withheld from the narrator. He knows all, sees all, and chooses when and where to reveal facts to the reader. The best way to make this interesting is to have the narrator follow a very unconventional style. Since he is all knowing, he is aware of his status as the narrator of the book and is thus able to be aware of the audience and comment personal feelings too them.
One example would be that of Tom Sawyer and Huck Finn novels, both of which are presumably told by the titular characters but are written down by Mark Twain. Huck Finn specifically points this out in the first chapter, saying that the story is his, just Twain is transcribing it and that's why his name is on the cover and not Finn's. Better known is that the character of Watson is transcribing the events of Sherlock Holmes, not the actual author, Sir Arthur Conan Doyle
Another popular convention, seen in Frankenstein and Dr. Jekyll and Mr. Hyde is a series of letters from the narrator retelling strange events as he or she witnessed them, but had no interaction with the characters during the course of events. The former uses one narrator detailing Dr. Frankenstein's story that was told while the Doctor was passing through. The latter was a series of letters from various witnesses to the stories events.
This is similar to the movie Chronicle, which is filmed entirely by camera presumably found after the incident and compiled. Also similar to Cloverfield which is presented as a singular unaltered footage of an incident which was recorded live. While the camera men and women in these films are real characters in the story, the "narrator" if you will, is the agency that released the film to the public, and will give further context such as the in universe name of the incident. An entirly real life style similar to this are a number of 9/11 documentaries. The History Channel Documentary 102 Minutes that changed America is a near real time retelling of the 9/11 attacks pieced together from archival footage shot from real amateur footage that were witnessing the events that was collected by the US Government and compiled by the History Channel. A similar documentary (name escapes me) from CBS was told from the perspective of two camera men who just happen to have been filming a documentary on the NYFD during 9/11 (Notably it contains one of three known footage of the plane flying into the first tower, and is the source of the most famous of the three).
Another option is that the narrator is in the story, but the narrator is significantly older than the character in the story. Examples of this include the Wonder Years and more recently How I Met Your Mother. The characters are recounting decades old events to the audience. How I Met Your Mother used this to great effect to allow for embellishment and out right lying as the Narrator openly admits that some events likely didn't happen, but that's how they were described to him OR is censoring the story for the Audience's benefit (namely his teenage children). Thus, the narrators have all the story knowledge through years of hindsight.
Another idea is the show version of the Trans-Siberian Orchestra's album Christmas Eve and Other Stories, in which a Narrator sets up a portion of the story that the next song is representative of. In the story, the narrator is himself recanting the tale told to him by another man, who may or may not have experienced the story first hand (although we come to learn that a portion of the events of the story take place in the very bar that the two men are presently in.).
The idea in all of these is that the Narrator is a second hand source to the events, rather than a first hand source. Thus, he or she is given more leeway in embellishment because, while the have seen some events, they had no effect on them. Rather, they reported on experiences related to this retelling. Here the Narrator is knowledgeable of all the facts of the story because the tale was told to him OR there are years of hindsight. Thus his withholding of information from the audience is not mean spirited as he is merely telling it as it was told to him. He would differ from an unreliable narrator because everything he says is distorted through both time, and another layer of storytelling, though he playfully could be holding back knowledge (as a great hook to continue reading).