True synonyms

I seem to remember reading somewhere that the only true synonyms in English are 'Gorse, furze and whin' which all mean exactly the same thing (a yellow-flowered shrub common in Europe, officially known as Ulex europaeus) and have no other meaning and are always completely interchangeable.

Can anyone think of any other words which mean precisely the same thing on every occasion, without even the slightest nuance of a difference?

DFG

Nil and zero? Twelve and dozen? Selfish and Republican?