Sly Marbo

"'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA!'"Sly Marbo is one of the deadliest soldiers of the Catachan Jungle Fighters in the Imperial Guard.

Official Canon
Even among the Catachan Jungle Fighters, Sly Marbo is uncannily skilled in survival, able to endure hostile conditions alone what would take a whole squad of men to defend against. He's been awarded the Star of Terra multiple times for his extraordinary service.

Despite being one of the few independent characters available to the Imperial Guard, Sly Marbo has very little fluff attached to him and has appeared on and off in various codices.

TTS Canon
Sly Marbo is a force to be reckoned with. He is the Imperium's avenging angel, appearing out of nowhere to slay mankind's enemies. He single-handedly rescued a feudal world from Dark Eldar raiders lead by Vraesque Malidrach, armed with just his combat knife, and freed the civilians from a deathtrap through the force of his rage.

Sly Marbo also had a brief appearance on the Slaaneshmas special.

Sly Marbo rescued Corvus Corax from a Catachan Barking Toad by leaping up into the air and knocking it off his head. He quickly departed, but remained in the background as the Catachan Jungle Fighters pledged themselves to the Primarchs on their journey to Terra.

Trivia

 * Sly Marbo's voice clip comes from the intro to the game Dawn of War, set to a loop.
 * The original art used for Sly Marbo had been the old official model, but the new version was an expertly painted high-definition model commissioned by Alfabusa from WarpStormPainting.
 * The ship Marbo's Glutes used by the Catachan Jungle Fighters is presumably named after him.