Real Knife

The Real Knife is a weapon item found in a gift box in Asgore's Home. Plot-wise, it is the Worn Dagger as seen through the lens of a Genocide Route. Its defensive counterpart is The Locket. It is the Genocide Route weapon item associated with the first human, and is implied to belong to them. 
When the Real Knife is equipped and used to FIGHT, it depicts a curled, red slash animation. This animation and sound effect it makes is shared with the Stick, Toy Knife, and Worn Dagger.
== Trivia ==
* In the Genocide Route, its existence is foreshadowed in Toriel's Home with the first use of red narration text. 
** The Check and Use flavor texts for the Real Knife reaffirm this.
* Name-wise, it contrasts with the Toy Knife found in the Ruins.
* Like The Locket, Real Knife has little use, as it is only obtained prior to fighting Sans, whose constant dodging and 1 HP both render it useless.
* The red slash animation and sound is preset at certain moments, regardless of the equipped weapon:
** It is the default animation when the protagonist attacks Photoshop Flowey.
** It is used to kill Flowey at the end of Neutral and Genocide Routes.
** On the Genocide Route, it is used twice when the protagonist attacks Sans during his "special attack."
** On the Genocide Route, it is used without the FIGHT option versus Asgore.
** It is used by the first human at the end of the Genocide Route.
* If the Real Knife is hacked into the protagonist's equipment on a non-Genocide Route, most monsters can be spared on the first turn, even if they cannot be spared normally. This is due to monsters automatically becoming spareable when the protagonist's next attack could easily kill them.
* Prior to the full release of Undertale, Toby Fox had denied the existence of the Real Knife.
* The Real Knife could possibly be a reference to Mother 3's Real Bat, since both weapons are found before the final battle and wielded by someone before the protagonist, and raise the attack stat to near 100.
== References ==
de:Echtes Messer
es:Real Knife
fr:Vrai Couteau
ja:Real Knife
pl:Real Knife
pt-br:Faca Real
ru:Настоящий нож
uk:Справжній кинджал
zh:真刀