CPU Water coolers
Water coolers are active coolers, but do not use air circulation for cooling, but instead use water. Special AIO (All-in-One) water coolers, such as the ARCTIC Liquid Freezer line, allow easy installation of the otherwise quite complex cooling system.
Since water is a significantly better heat conductor than air, water coolers are usually more powerful and nonetheless quieter than regular active CPU coolers. The higher costs and the high space requirement in the system are the main disadvantages.