Wireless Sensor Networks (WSNs) consists of large number of spatially distributed configurable sensors, to meet the requirements of industrial, military, precision agriculture and health monitoring applications with ease of implementation and maintenance cost. Transmission of data requires both energy and quality of service (QoS) aware routing to ensure efficient use of the sensors and effective access of the gathered information. Design of WSNs considering its issues is challenging task and leads to complex algorithm design which are difficult to analyze by analytical methods and by physical measurements. Deploying test-beds supposes a huge effort. In deed Computer aided simulation is the feasible approach for analysis of WSNs. We addressed different types of simulators along with their key features and their applicability for simulation in numerous application areas.