Wireless Sensor Networks (WSNs) consist of a large number of wireless sensor nodes networked together. It is a complex set of applications, link technologies, communication protocols, traffic flows and routing algorithms. Simulation is a predominant technique used to study and analyse the performance and potency of a senor network design. Since there are a huge variety of simulation tools available for WSNs, which vary in their characteristics and capabilities, it is often very difficult to decide which simulation tool to choose and which one is more appropriate for large-scale WSNs. To address this issue, in this paper, we review some of the most widely-used and state-of-the-art simulation tools for WSNs. This distinguishing feature of this paper is that we identify the key limitations of the reviewed simulation tools and inspect their suitability for large-scale WSNs. We review and investigate simulation tools based on a new set of preferred criterion, i.e. popularity, accessibility (open-source), complexity, accuracy, scalability, extensibility and availability of various models and protocols.