I want to get Gill Sans working as the sans serif font of my LaTeX documents, but I have yet to find a way of doing this, even though it is installed on my system.
In my search for a solution I came across the following paper by Gerben Wierda, Thomas A. Schmitz and Adam T. Lindsay:
http://www.tug.org/pracjourn/2006-1/wierda/wierda.pdf
It seems clear that they did the piece of work that I want, and they even detail how others might recreate their success. Unfortunately I have not the foggiest idea of what most of it means.
At first I thought it would be as simple as including the command \usepackage{gtamacgillsans}, which was one of the products of the paper, but I was proven wrong immediately by an error-message from pdfLaTeX. I suppose this has to do with me not using Gerben's TeX distribution, but I am not really sure.
At any rate, I really hope someone might spoon feed me the contents of the paper so that I might do the things they did to get Gill Sans working, because I wouldn't even know where to start otherwise. My starting point seems to be vaguely similar to theirs (operating system, font already installed), even though it's now 8 years later.
If not, at least give me a firm ``It can't be done''.

fontspec. – egreg Oct 18 '14 at 08:01\usepackage{fontspec}\setmainfont{Gill Sans}, works withLuaLaTeXas well. (Just a showcase, you can use this locally by passing the command\fontspec{Gill Sans}to the compiler.) – 1010011010 Oct 18 '14 at 08:37gtamacfontspackages with pdfLaTeX or ConTeXt. However, I don't know whether the package is available and I don't know whether you could do this with current versions of the fonts. (The packages were designed to use truetype fonts.) Gill Sans has definitely changed since the name of the font I have isGill Sansand notGill Sans MTas reported in Mico's answer. Xe/LuaLaTeX will definitely be more straightforward if that's an option and unless you have older versions of the fonts. – cfr Oct 18 '14 at 14:00