Yes, intelligence agencies have sometimes used sex as a means of gathering information. Here's how it works: spies or assets (people who provide info to an intelligence agency but are not spies themselves) will seduce a target such as a high-level policymaker, businessman, or person who defected to an enemy country. They will then use that relationship to gain that target's confidence. From here, several different things can happen:
The target may trust his/her new paramour with sensitive information, which is then relayed back to whatever agency the spy works for.
The spy may lure the target to a location where they can be captured and interrogated.
The spy may blackmail the target for information.
This strategy is known as the "honey trap," and spymasters have used it to great effect more than once. Here is a very entertaining Foreign Policy article with a few examples of famous honey traps during the Cold War. One of the most famous was when Markus Wolf, the head of the Stasi throughout much of the Cold War and one of the greatest spymasters in intelligence history, assigned dozens of male East German agents to seduce female West German bureaucrats. In doing so the Stasi managed to infiltrate multiple layers of the West German government.
Are you speaking in the context of rape as a weapon too? If so I'd be happy to elaborate/ add sources.
Mata Hari http://en.wikipedia.org/wiki/Mata_Hari
Was a well known exotic dancer and courtesan in the early 1900's and was convicted of espionage and spying for the Germans during World War One, which she was executed for in 1917. Earlier she was also suspected of possibly being a double agent.