More Passive-Aggressive Mobs

Mojang has previously stated that all Hostile mobs have to be fantasy based. I think that makes sense, but there does seem to be a bit of a Gray area, in which mobs are normally Passive, but under certain circumstances will Attack/Damage the Player.

For example, Puffer Fish will poison the player if they get to close, and Polar Bears will attack the player if they have some cubs with them.

I think there should be more mobs like these, mobs that aren't necessarily "Hostile" and won't seek out the Player, but can still be dangerous.

Some examples I'd like to see:

Rattle Snakes that spawn in Deserts, which would rattle their tail if the player starts to get to close, and will attack if the player continues to get closer.

More Bears, namely Grizzly Bears or similar that would spawn in Forests.

A  larger type of Cat like Lions or Cheetahs that spawn in jungles could be cool to see, though that might lean to much towards being a Hostile mob.