Saw a Youtube video about a Tu-154 that suffered a total electrical failure over the trackless forests of Siberia. They used a glass of water as an attitude indciator....
I once had a student who claimed her sense of balance was so good she could keep the airplane righside up with no attitude reference. So one hazy gray featureless day we went up with a plastic bottle half full of drinking water taped upright to the instrument panel. I put soap stickers over all three gyro instruments and the altimeter, and she put the hood on and told me she would let me know when the plane departed straight and level flight. I eased in a little very gentle left rudder pressure and the plane very gradually eased into a spiral to the left. As the bank angle gradually increased the nose crept below the horizon and the airspeed gradually crept upward. As it did, I smoothly eased the throttle back to keep the engine and prop noise constant. As the bank angle approached sixty degrees and the Gs approached two she said: "You've pulled us into a climb, you tricky bastard!" By this time the nose was well below the horizon, the airspeed had increased by fifteen knots, but I had kept the RPM constant by gradually reducing throttle, and the water in her bottle still indicated straight and level.
At that point I said "Raise your hood, it's your airplane", while bracing my arms to prevent her pulling too hard on the yoke. She showed good airmanship by smoothly rolling wings level, pulling the nose up, going to climb power and pointing us back at the airport, AND THEN giving me what-for.
"There, you slimy bastard! Aviate, navigate, communicate; now it's my turn!", whereupon she ripped the water bottle off the instrument panel, beat me over the head with it, then dumped its contents all over my shirt, laughing her ass off. "When we get back, I'm gonna buy you beers til you fall down. Hubby'll come get me, but you'll be stuck there, 'n you're gonna need that sleeping bag you keep in the ground school closet! Good thing tomorrow's your day off, 'cause you won't be airworthy!"
She went on to a lucrative airline career and retired quite wealthy, spunky sense of humor unabated. One of my more satisfying success stories.