Nexus 4 fragile glass
I've dropped mine quite a lot and it hasn't broken. Admittedly the drops tend to be on softer surfaces like carpet or wooden flooring but they do so at quite a speed as I stupidly stand on the charging cable and send it flying when I stand up. In fact the only damage it's sustained is a small <10mm long dent where the colour has also been knocked off. I was expecting the screen or back to be cracked or scratched when I saw that but they're both fine.
Do I want another phone with glass back? Hell no! This thing is ludicrously slippy on any surface! They could use Nexus 4s as lubricant for large machines and see massive improvement.