A regular round cooler with a fan in the center. Nearly noiseless.

A similar cooler, just the heatsink color is different.

This cooler has a differently shaped heatsink. Nearly noiseless.

This cooler has a larger heatsink of yet another shape which is also cooled by a fan in the center. The fan's rotation spees is low, so the cooler is noiseless.

A regular round cooler with a fan in the center. Nearly noiseless.

This cooler is larger, though is still fits into a single expansion slot. The fan is not in the center, but it doesn't have a cover to direct airflow. Nearly noiseless.