This may not be everyone's experience, but I have been "lucky" enough to be choked out accidentally during some sparring sessions.
It doesn't always happen this way, but when it does it's insightful: I first get a very strong sense of "Wrong," as my understanding of the laws of physics vanish. If the choke has finished and I'm left standing but still going to black out, I'll probably topple at this point as I misunderstand gravity and forget about/lose control of my legs.
Enough of my ego will still be aware enough to have the thought "this is embarrassing, I've fallen," but it fades quickly as I lose understanding of why falling is bad, what embarrassment is, and what ground is. Then there will be a fading out of visual input (auditory goes before anything else), with my awareness quickly shrinking to a tiny ball of awareness, which visualizes itself as a bright speck of light surrounded by nothing. Panic will still exist and set in, as the speck loses subsystem after subsystem, not quite sure what is being lost but knowing things are, and feeling an encroaching blackness.
Eventually the only thing left is a feeble desire to not vanish, followed by nothing.
This might actually happen every time I get choked out, but only the right circumstances allow it to be "written" to memory.
It aligns with what friends have told me about near death experiences (heart attacks, overdose).