I have never heard or seen this as a phrase outside of people actually doing that to animals (attaching a horn to a horse).

To me it means nothing at this point in time.

If I had to decide what it should mean, given the field of work I'm in, it would be to make something worse. In IT we don't want unicorns, we want cattle =} ... things that are "normal" and easy to maintain, not "special" and difficult to come by.

It depends on the conversation and with whom you are talking. Generally speaking "yes" in implies making something better and special. BUT the word "unicorn" has several gay and sexual references, just an FYI.

It means to make something better. To improve it

Dean O'Donnell,

Do you mean the phrase may mean to turn someone into a gay?