I fall asleep fairly often while gaming.
Most recent occurrence was in EVE. Mission-mining in a backwater highsec system. The safest way to mine, really. EVE regularly spawns "rats", aka NPC pirates, and they're a rather sorry bunch in highsec. Easy Drone fodder if they're out and set to auto-aggro.
What can I say, long story short, damn rats shot me to pieces. Must've taken half an hour or so. Woke up to the hull breach alarm and got to watch the pretty explosions. Death by a thousand paper cuts,
At least it was only a pimped Retriever, not that bad; but still, it stinks.