Here are the sub-genres of the Suspense & Thriller category:

Action: a story that often features a race against the clock, lots of violence, and an obvious antagonist.

Comic: a thriller played for laughs, whether through a spoof of the genre or wisecracking interplay between the protagonists.

Conspiracy: a thriller in which the hero battles a large, powerful group whose true extent only he recognizes.

Crime: a story focused on the commission of a crime, often from the point of view of the criminals.

Disaster: a story in which Mother Nature herself is the antagonist, in the form of a hurricane, earthquake or some other natural menace.

Eco-Thriller: a story in which the hero battles some ecological calamity and often has to also fight the people responsible for creating that calamity.

Erotic: a thriller in which sex plays a major role.

Espionage: the classic international spy novel, which is enjoying a resurgence with one important change: where spies used to battle enemy spies, they now battle terrorists.

Forensic: a thriller featuring the work of forensic experts, whose involvement often puts their own lives at risk.
Historical: a thriller taking place in a specific and recognizable historic period.

Horror: a story—generally featuring some monstrous villain in which fear and violence play a major part, complete with graphic descriptions.

Legal: a thriller in which a lawyer confronts enemies outside as well as inside the courtroom, generally putting his own life at risk.

Medical: a thriller featuring medical personnel, whether battling a legitimate medical threat such as a world-wide virus, or the illegal or immoral use of medical technology.

Military: a thriller featuring a military protagonist, often working behind enemy lines or as part of a specialized force.

Police Procedural: a crime thriller that follows the police as they work their way through a case.

Political Intrigue: a thriller in which the hero must ensure the stability of the government that employs him.

Psychological: a suspenseful thriller in which the conflict between the characters is mental and emotional rather than physical—until an often violent resolution.

Romantic: a thriller in which the protagonists are romantically involved.

Supernatural: a thriller in which the hero, the antagonist, or both have supernatural powers.

Technological: a thriller in which technology usually run amok is central to the plot.

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SOURCE: "Sub-Genre Descriptions" by Michael J. Vaughn, Writer's Digest, March 18, 2008.