The best samurai swords are made with several types of steel.  Hard on the outer layer, soft in the inner.  The hard steel is necessary to ensure the sword can actually do what it’s supposed to do – cut and kill.  The soft steel gives it flexibility to prevent if from breaking.

I’ve thought this an apt metaphor for development and growth.  In my experience, some of the best people I know follow this model – tough but kind.  What I really despise is the opposite.

If not into swords, then the king of fruits – the durian.  Notwithstanding its really uncalled for reputation (it’s delicious, I promise), it’s the same concept – spiky outside, soft inside.  Don’t mess with the durian, falling ones can put you in a world of hurt.