True story - one night my loud downstairs neighbors had a shouting match at 5am that woke me from a dead sleep even with my loud portable A/C on. I was just about to get really annoyed, get up from my bed and tell them to shut the eff up when my cat climbed onto my pillow above my head, laid his head down on my the side of my head just above my ear and started purring. The vibrations from the purring against my skull actually drowned out the yelling and screaming and I was able to go back to sleep.
I had a cat who used to climb on top of my shoulder (I sleep on my side) and stick his nose in my ear and purr. And sometimes drool.
Gotta love 'em.