Petra Janecek's revolver
From Halopedia, the Halo wiki
During an expedition to Karava in March 2558, Janecek used it to kill the Sangheili 'Lordan when he threatened her comrade, Spartan Naiya Ray. Later that year, she threatened to shoot Benjamin Giraud with her revolver after he uploaded a personal conversation between the two of them online that could possibly incriminate her. She exaggeratedly claimed that the next time she saw him, she would shoot him with her revolver. Janecek later forgave him.
The revolver design is likely based on the real-world iconic 19th century Colt Single Action Army, though it is unknown if the two share a connection in-universe.
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