[Xaccers]

When your brain starts suffering oxygen starvation, you get tunnel vision and flashes of light, along with the endorphins released making you feel calm and loved. Most fighter pilots experience this just before they black out during high-g training.
It's quite interesting.

Personally I've had a NDF, after a car accident I crawled out and found it was hard to breath, I'd broken some ribs.
I lay down and stopped breathing.
I felt warm and calm, and there were voices saying the names of my family members, none of who are worth living for. Another voice was telling me to give up, take the easy route for once, I've struggled enough.
Then a booming voice said "Kate" (someone who I mistakenly thought was a good friend at the time), and I sat up taking a huge breath which hurt like buggery and vowed not to die until I'd seen her again.
So, next time someone religous makes a flippent comment that you never get an athiest on their death bed, slap them for me as I find that comment extrememly offensive.