This paper describes NCTUns, an innovative network simulator and emulator for wireless and mobile networks. Effects of various radio resource management and quality of service (QoS) schemes on higher-layer protocols and real-world applications can be easily studied using NCTUns. In this paper, we elaborate on NCTUns simulation methodology, architecture, design, functionalities, performance, and applications. NCTUns simulation for wireless ad hoc, sensor, inter-vehicle communication networks, GPRS cellular networks, and wireless mesh networks are also illustrated. More details about this tool can be found in http://NSL.csie.nctu.edu.tw/nctuns.html.