Crafty Games' Spycraft 2.0 takes many of its core cues from Dungeons and Dragons 3.X, but adds granularity in its skill system and introduces several Dramatic Conflict minigames.
Spycraft 2.0's social skills expand the Bluff, Diplomacy, Intimidate, and Sense Motive of Dungeons and Dragons 3.X to Bluff, Impress, Intimidate, Manipulate, Networking, Resolve, Sense Motive, and Streetwise, plus, arguably, Cultures and Bureaucracy. How to use each of skill is explained in (some say ridiculous) detail; the skills section of the Spycraft 2.0 rule book is over 80 pages compared to the 25 in the Dungeons and Dragons 3.5 Player's Handbook. It's not just a matter saying, "I roll my Bluff skill to lie about having a monkey in my pants," but a whole cascading series of lying-about-a-pants-monkey rules that makes a high result feel just as rewarding to those who've invested in their social skills as a a high combat result does to those who've invested in dual-wielding chainsaws (which a character can also do in Spycraft 2.0, by the way)
Dramatic conflicts expand the skill system to give cinematic montages depth. In these mingames, an evocatively-named strategy--access to which is limited by the character's ability scores, other statistics, feats, skills, and so on--printed on a card is chosen in secret by both sides in the Conflict (usually by 1 player and opposed by Control, the guy running the game). Cards are revealed, dice are rolled, effects are tallied, and the range of effects are wide. Social Dramatic Conflicts include brainwashing, infiltration (abstracted ingratiating of one participant into an organization a la most episodes of Burn Notice), interrogation, and seduction (often misunderstood as sexual but really code for turning another to one's side a la the film Training Day). Probably manhunts are social, too, but in an entirely different way.
If you want mechanics not judgment calls Spycraft 2.0 details exactly what happens every time someone rolls. There is no make-crap-up phase except to narrate the effects of what the dice have already said happens.
The dark side is that the game's a murder weapon, clocking in at nearly 500 pages. The text is dense and has high expectations, desperately wanting its reader to enjoy charts and tables as much as it does. It's extremely mechanized, providing rules for life. It works best with just one kind of play--it is mission-based, resisting sandbox-style games and stifling attempts by characters to take out payday loans for nuclear ransoms. But, despite all this, it's a robust, powerful system that puts social interaction and physical combat on nearly equal footing with mechanics that make both interesting.
A third edition of Spycraft is in the works, and while Fantasycraft was interesting it lacked the borderline-OCD rule-for-everything absurdity of Spycraft 2.0's ruleset. With Fantasycraft's style--a looser skill system lacking in Dramatic Conflicts--a blueprint for third edition Spycraft, you shouldn't wait for third edition and instead get Spycraft 2.0 if you want a seriously rules-heavy system that details social interactions and choking out unsuspecting guards in near-equal measure.