Other - I'll have a fan on if it's hot out, or our little space heater (which also has a fan) on if it's cold, because I want the temperature to be comfortable. I *hate* the sound of both, and find it distracting when I'm trying to fall asleep. I'd rather be annoyed by noise than be an uncomfortable temperature though.
I need air circulating in the room, it's usually hot at bedtime, and the noise helps in muffling the rest of the household (which is as sound-proof as a tent). My ex-husband couldn't stand it, so he snored as loudly as he could all night.
I don't need a fan running to be able to fall asleep. Though after running my ceiling fan all summer then shutting it off when it gets cooler, it does take me longer to fall asleep until I get used to it being silent without the fan, or from hearing other noises (like a snoring dog) that I didn't hear when the fan was running.
I have a ceiling fan and I use it at night because my baby gets stuffy at night. Plus being upstairs it gets so hot. Even with the heat on so need something to circulate. If not the fan I use a humidifier because of the dry air.