What properties does Titan have, that make it unique among Solar System moons?

This mammoth moon is the only moon in the solar system with a dense atmosphere, and it's the only world besides Earth that has standing bodies of liquid, including rivers, lakes and seas, on its surface. Like Earth, Titan's atmosphere is primarily nitrogen, plus a small amount of methane. It is the sole other place in the solar system known to have an earthlike cycle of liquids raining from clouds, flowing across its surface, filling lakes and seas, and evaporating back into the sky (akin to Earth's water cycle). Titan is also thought to have a subsurface ocean of water.