This paper presents JSensor, a parallel general purpose simulator which enables huge simulations of Wireless Sensor Networks applications. Its main advantages are: i) to have a simple API with few classes to be extended, allowing easy prototyping and validation of WSNs applications and protocols; ii) to enable transparent and reproducible simulations, regardless of the number of threads of the parallel kernel; and iii) to scale over multi-core computer architectures, allowing simulations of more realistic applications. JSensor is a parallel event-driven simulator which executes according to event timers. The simulation elements, nodes, application, and events, can send messages, process task or move around the simulated environment. The mentioned environment follows a grid structure of extensible spatial cells. The results demonstrated that JSensor scales well, precisely it achieved a speedup of 7.45 with 16 threads in a machine with 16 cores (eight physical and eight virtual cores), and comparative evaluations versus OMNeT++ showed that the presented solution could be 43 times faster.