Ada Wong (Resident Evil 2)

Leon stumbles upon this mysterious woman who is quite secretive yet, at the same time, a professional and skilled investigator. She can also come across as condescending, and has a tendency to talk down to those she deems inferior to herself.

Ada's true intentions are unknown until the very end, however she proves to be useful in a gunfight. There are two points in the game where you gain control of her, and neither of them are for very long. The first time is when you reach the Sewage Disposal Facility, and you help Ada crawl through a ventilation tunnel. The second time is in the Sewer Basement, when Leon gets shot by Annette Birkin.