Allied Mastercomputer (I Have No Mouth, And I Must Scream)
Bender Bending Rodriguez (Futurama)
Dr. Nefarious (Ratchet and Clank)
HK-47 (Star Wars: Knights of the Old Republic)
KOS-MOS (Xenosaga)
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HK-47: The very best there is when you absolutely positively have to kill every meatbag in the room. Accept no substitutes!