City crisis simulation (e.g. terrorist attack)
WP: Computers simulate terrorist extremes
Los Alamos scientists are running terrorist attack/response simulations. Well, the article title is misleading, they're not simulating terrorists (which would pose a whole set of interesting questions about scientific knowledge, social construction and security), but rather, the impact on telecomm, health, and infrastructure systems. They're using the standard justifications for systems simulation: these are big, highly complex, highly interdependent systems that are ill-understood and have had drastic domino-effect collapses before (like the northeast power blackout).
The article also talks about epidemiology simulations (smallpox in this case, following the terrorist scenario again) that take into account the interactions of individual people with each other -- very much along the lines of agent-based simulations, and satisfying complexity theory's arguments about tipping points and emergent effects. [The article doesn't seem to say whether they actually computed at the level of individual agents, or used statistical aggregate approximations.]