Zeal got it. You want a plastic that is impact-resistant, I.e. bends instead of cracks if it is bent.
We call such a material property "toughness". It's the area under the stress/strain curve and represents how much energy a material can absorb before failure. Diamonds have high (very high) young's modulus, but very low toughness: you can crack them with a hammer (they also burn. I've never been a fan). PBT is the same way (you can look up the destructive hammer test for PBT)
As far as other materials, assuming cost is no object, PC/ABS blends were very popular for computer cases a few years ago, now it seems everyone has moved to magnesium (which has similar issues to PBT: It's not ductile enough for my taste) or a fiber reinforced PC/ABS blend. The reinforcing fibers sacrifice some durability in favor of much higher strength: it's really up to the use case if this is a good idea or not.
I'd like to see a FR-PC+ABS keyboard case, but I'm not sure it'll be cheap enough.