Ah yes, redundant - maybe, but doesn't it generally imply that at some point it has been of use? Perhaps the word I'm looking for is superfluous?
It can, but it needn't. All it strictly means is 'something whose removal would make no difference'. In the context of everyday language, where it's most often used in the context of redundancy payments and the like, it's gained an overtone of 'no longer needed'; but strictly it simply means 'not needed'. 'Superfluous' is very similar, but to me at least superfluous suggests 'more than enough', rather than simply 'unnecessary'. Superfluous decoration, to me at least, suggests that
some decoration is needed...just not this much.
Both, in any case, remain adjectives. A word that performs no function or is unnecessary is not 'a redundant' or 'a superfluous'. We're still no closer to a noun.