At national cook-offs, the ingredients are guarded like a national secret. Some will hint at the special ingredient, others will claim they will go to their graves before they even hint at what gives their chili its special flavor.
Over the years, I have heard of a variety of "secret" chili recipe ingredients, and tried a few myself. One of my favorites is baking cocoa; it helps to balance the acid in the tomatoes.
I have also tried a couple of tablespoons of honey from my beehives. If you like tang, use a couple tablespoons of lime juice, it gives the chili a little spanish twist.
Want a little nutty taste? Try peanut butter. I experimented with both regular and light and couldn't tell a difference so I would pick the lighter version.
Don't forget cooking with beer. Cooking removes the alcohol leaving the taste of the different hops. Try different beer varieties until you find one you like. In the chili, I mean, and not all together!
What is your secret chili ingredient?