What year was the Wendy's Spicy Chicken Sandwich first made available for sale?
Wikipedia's article on Wendy's says it was added to the menu full-time in 1996, and was a promotional thing before then. There's no source given, unfortunately, but I found this 1996 shareholder report saying "This year we added two permanent additions to the menu -- the innovative Spicy Chicken Sandwich...", and on youtube you can find tons of copies of their ad marked as being from 1996.
I think it was first sold as a promotional thing in 1992, but I didn't find a really solid source yet. The best I've found is this ad for the new spicy chicken sandwitch marked as being from 1992.
The Wendy's Story says it was in April 2004.