Publisher Summary The aim of this chapter is to elucidate the special types of heat pipes. The variety of heat pipes, in terms of their geometry, function and/or the methods used to transport the liquid from the condenser to the evaporator, is remarkable. Some types of heat pipe have become less popular over the decades or have ceased to be regarded as special. Other types have seen a re-awakening of interest, brought about by demands for increasing miniaturization and the need to enhance performance, in particular liquid return flow rates. This chapter presents detailed accounts on variable conductance heat pipes, which have the ability to maintain a device mounted at the evaporator at a near constant temperature, independent of the amount of power being generated by the device; thermal diodes, which are crucial components of renewable energy systems; pulsating heat pipes, which is used in electronic cooling systems; micro-heat pipes, which are used in medical fields. This chapter also describes the use of electrokinetic forces. Some electric field effects that could be used to assist heat pipe performance include electroosmosis, electrohydrodynamics (EHD), and ultrasonics.