Naaman
Veteran Sergeant Naaman was a Dark Angels special character back in the third edition
Like a certain other pretender Naaman was a Scout sergeant, but has been around in the fluff for a LOT longer and he did have his own model and his own special rules.
However, suddenly he vanished and has not been seen since. Though he has not been completely forgotten about and was the protagonist of the novel: Purging of Kadillus which involved his most famous (and final) campaign against the Orks on Piscina.
He was not necessarily the best Scout sergeant to have ever lived (evidenced by the fact they killed him off), but he was made Awesome by the way they portrayed him; in the novel Belial was frustrated by his insubordination, that he would frequently do whatever he felt like, though to usually great effect regardless.
Ravenwing Sergeants would also defer to him, though in his original rules he was a member of the Deathwing, so that explains that.
History
According to the official records Naaman lived from 823-997.M41, so a reasonable lifespan for a Space Marine at least.
After the initial repulsion of the Dark Angels forces movements against the Orks on Piscina IV, he was the only one to suvive the cunning counter-attack of Nazdreg yet he returned to the Dark Angels' base of operations and later managed to lead a team of Scouts through the Ork lines and sentries to discover and relay information about the tellyporta systems used by Nazdreg to such deadly effect.
Then later when he was holding off the counter-attacks from within Nazdreg's base, he was able to direct the Deathwing to remove an energy relay from the teleportation base, presumably in order to disable it. Unfortuately he was eventually killed by an exploding Ork Deff Dread. But his name was added to the Book of Honour for the Dark Angels.