I had a dream in which I was sitting on a train and talking to an ostensible coworker (nobody I know in real life) about programming languages and some of the interesting stuff going on in performance evaluation, when suddenly she asked me, "Dude, are you okay?"
"Then why are you turning bat-cave black?"
I suddenly realized that I was turning blue with hypoxia, and promptly woke up to find myself not breathing.
After a few seconds of hyperventilation, my first thought was: "Uncaught exception propagated up the stack."
(I'm fine, but a bit concerned as I have no idea what happened. Also, now I have a headache. Chris did once comment about how I'd stop breathing in my sleep but didn't snore, so this has been going on for a long time in any case — probably the only reason I noticed this time was that the context was interesting enough to, er, trip my monitoring. I don't think it was sleep apnea, as I was sleeping on my side and it didn't feel like an obstruction, and technically the fact I woke up makes it by definition not sleep apnea.)