AnyLogic - AnyLogic has changed simulation modeling and expanded its application into complex business environments. The unmatched flexibility of multimethod modeling allows users to capture the complexity of virtually any system, at any level of detail.
FlexSim - Simulation software to model, simulate, predict, and visualize systems in manufacturing, material handling, healthcare, warehousing, mining, etc.
ns-3 - a discrete-event network simulator for internet systems
Simio - Facility design simulation & production scheduling
Paessler Multi Server Simulator - Paessler Multi Server Simulator is inexpensive and robust software that helps you power massive-scale testing.
Arena Simulation Software - Arena Simulation Software is an intuitive simulation software solution that helps you arrive at the right decision at the right time to help you ripe the best for your business.