Putin says Russia was ready to activate nuclear arsenal over Crimea

[Man from Pickens]

47. We've been doing exactly that for years

http://www.wsws.org/en/articles/2006/04/iran-a13.html

and we're not the only ones - Israel makes nuclear threats regularly

and India has done the same (against Pakistan):
https://www.wsws.org/en/articles/2013/05/10/shay-m10.html

So has Pakistan (against India).

And believe it or not, China has made this same threat against the US (multiple times). If you don't read international news sources like I do, you probably weren't aware of it. Here's an example http://www.asianresearch.org/articles/2718.html

Your conception of a world without overt nuclear threats between nuclear states and also against non-nuclear states is not even slightly correct. Every nation which has nukes (possibly excepting France) has threatened to use them in at least one specific circumstance directly tied to what it views as its vital security interests.