From the comments on this page it looks like "a scissors" is acceptable in Ireland and in the American midwest. However, the research I did on 'scissors' confirms that they should be treated as a plural. So, if you are here to learn English it would be preferable that you go with the latter school. If you already use or have heard people using 'a scissors,' there is an explanation for that in the etymology of the word, and it relates to the fact that in German they say, "eine Schere." Google it -- it's interesting.
Perhaps you're speaking British English? I've been speaking American English since I was born over 60 years ago, and I have never used "a scissors". I have used "scissors", or "the scissors". The only time I've used the indefinite article "a" was as part of the phrase "a pair of scissors".
Agreed, because "a scissors" is also acceptable usage in US English. See Merriam Webster, which specifies "noun plural but singular or plural in construction." [ http://www.merriam-webster.com/dictionary/scissors ]
Nope. In Canada, we would never say "a scissors." We will say, "a scissor lift" (a mechanical lifting device for large loads), but we would never refer to a pair of scissors as "a scissor."
Also, regarding the link above, there is nothing to indicate that "a scissors" is acceptable in US English when referring to a pair of scissors. It's singular in construction only when used as "a scissor lift" or "a scissor hold".
Yes, Domleschg included a link to a page that he neither fully understood nor read. Merriam Webster goes on to explain, '"Scissors is an example of a plurale tantum, or an English word that only has a plural form that represents a singular object. Though pluralia tantum name single objects, they are grammatically plural: "the scissors are on the table," "my pants are in the dryer."' "Noun plural in construction" refers to the morphology and etymology of the word, which they explain on another page that is attached via a link. Plural in form means you must treat it as a plural and use plural articles and verbs with it. Therefore, "a scissors" is not acceptable in American English.
It grates seeing an indefinite article used with a noun ending in -s (a glasses, a trousers, etc). Also, 'any' is the norm in questions, rather than 'some' (though of course there are exceptions), but it wasn't accepted by DL either... one never knows if the owl wants a literal or idiomatic translation.
Scissor isn't generally used as a noun. Instead scissor describes the shearing caused by two surfaces scraping or dragging across each other in opposite directions. Scissors is the noun normally used to describe any tool purposely built to use this motion, generally for cutting. This is the same for shears, which are just larger scissors :)
I don't think it's technically incorrect, but it would sound unnatural in conversation.
Some people also consider each individual blade of scissors has a singular scissor.