Gamora's Switchblade is a collapsible blade that was used by Thanos to demonstrate his idea of balancing the universe to Gamora. It includes dual blades that appear on both sides of the knife that connect to the hilt.
While half of the Zehoberei species were ready to be killed by Thanos, Gamora attempted to hide with her mother, but was quickly found by Thanos' soldiers. Gamora fought off the soldier restraining her, an act that Thanos himself saw, earned the Titan's interest in her. He took her aside and used his red and silver switchblade to teach his beliefs on balance by symbolizing it with balancing the knife on his finger and asked her to do the same. When his soldiers began the massacre, Gamora turned and almost saw her people massacred. However, Thanos turned her attention back onto the knife and complimented her when she balanced the switchblade.
Many years later, Gamora had joined the Guardians of the Galaxy and after gaining information of Thanos' plan to wipe out half the universe, she went to Knowhere where the Reality Stone was. Arriving at Knowhere, the Guardians then headed to the Collector's Museum to find Thanos threatening the Collector and demanding to know where the Reality Stone was. Sensing an opportunity, Gamora attacked Thanos, stabbing him in the neck with Godslayer and then plunging the switchblade into his chest. As Thanos died, Gamora broke down crying. As she did, Thanos' voice rang out, telling her that he was sure she still cared about him. The Reality Stone revealed the true nature of Knowhere; burning and destroyed with Thanos reappearing. Thanos took Gamora hostage and the Guardians attempted to save her, but Thanos used the Space Stone to transport away from Knowhere.
After Gamora had suffered from watching Nebula being tortured, she reluctantly led Thanos to a planet called Vormir, where they met the Red Skull who guided them to the obtain the Soul Stone. Red Skull explained to Thanos that he needed a sacrifice of a loved one to be given the Infinity Stone, by throwing that person off the cliff to their death. Gamora, upon hearing this, unleashed her bitter resentment for Thanos. Thanos turned around and told Gamora that he needed her to be the sacrifice. Gamora quickly attempted suicide by using the switchblade to stab herself but Thanos easily turned her dagger to bubbles. Thanos tearfully apologized, dragging her over to a cliff and threw her to her death.
Gamora's switchblade was a knife that had two dual blades on each side, since it can be used as a weapon, she was able to stab through Thanos' chest, though it was an illusion.