This knife belonged to Chance, one of the Great Khans and a prominent character in the graphic novel, All Roads. The blade is still stained by the blood of the Fiends it last killed at the tribal village. With a Melee Weapons skill of 100 and all of the damage and attack speed boosting perks, its DPS becomes as prominent as Oh, Baby!, which is an outstanding feat, considering it has 5% of the weight (2.5% with Pack Rat). The only downside is that the lower DAM makes it more vulnerable to high-DT enemies (offset somewhat by poisons). Also, because of the fact that it is near Goodsprings, if the player can survive the nearby cazadores (see below), this weapon can be had at a very early level.
Chance's knife qualifies as an improved holdout weapon, meaning that if the player has a Sneak skill of 50 they can carry it into casinos and other restricted areas.
Assassin - The Caesar's Legion assassin sent to kill President Kimball carries a special version which is non-playable. This prevents the weapon from normally being shown in inventory, e.g. when pickpocketing the assassin. The weapon is otherwise identical to the standard combat knife.
Cass - Rose of Sharon Cassidy carries a special non-playable version of the weapon, also otherwise identical to the standard version.
It's located in Chance's grave, north of Goodsprings, on a hill near the Tribal Village along with Great Khan simple armor. A shovel is needed to access the loot. Once at the tribal village, backtrack towards the main road while looking south. You should see a path leading up the hill and at the top is Chance's grave.
Chance's knife, like all combat knives, gets the damage bonus from both the Cowboy and the Grunt perks, making it the only Unique weapon that benefits from both perks.
The Elijah's Ramblings perk (Dead Money) will completely offset the critical damage penalty of the Heavy Handed trait, letting the knife utilize its full critical damage and the bonus damage of heavy handed if used simultaneously.
The blood stains on the knife are most likely from Chance's duel in the tribal village.