I still miss Zantigos. I think I had my last cheese chilito from them around 1987. I understand there’s a few in the Minneapolis area.
Reddit posts questions about “what discontinued food products you miss” so much I have a text file prepared which I cut and paste in order to answer. I will share it here as well:
Restaurant products: Pizza Hut Edge pizza; McDonald’s Chicken Fajitas; Burger King Italian Chicken Sandwich; Burger King Chicken Burger; Burger King Tacos; Dunkin Donuts Orange Coolatta made with Orange Juice as well their Lemonade and Arnold Palmer Coolattas
Store products: Chicken Helper Teriyaki; Chicken Helper Sweet And Sour; Campbell’s Tomato Cup of Soup; Jello Pudding Pops; Walmart’s store brand fudgsicles; Freezer Queen meat & gravy pouches; Campbell’s Ravioli-Os
The Burger King Italian Chicken Sandwich is a good one. Forgot all about those.
I wish Subway still offered the “seafood sub”*, which was loosely based on fish and probably contained artificial crabmeat and other artificialities, but was still good with the appropriate add-ons, if you made sure they didn’t glop extra mayonnaise on it. I used to get it for lunch at work. A footlong seafood sub with a bag of chips wasn’t a healthy eating spectacular but was enjoyable anyway.
*as of '23 it’s supposedly offered at selected locations, but I haven’t seen it on the menu in a long time.
There are several fast food places that I would like to see come back. And several discontinued items or cooking methods (beef fat fries, milkshakes with actual ice cream, actual spices) or the vanishing value menus.
What specific items depends on the place. I liked the smoked meat sandwiches at Costco. I miss JW Kwinter’s, an amazing Toronto hot doggery and deli, maybe not so well known. Not many chains now serve good fast food fish, and the fish sandwich at Harvey’s was very good.
As was mentioned way back in the original version of this thread, KFC’s chicken littles. Great sliders. In high school I could get 3 littles and 2 biscuits for $3.
They have something called a chicken little now, but it is just a tender on a bun.
BK brings it back as a limited-time-only item every year or two. In fact, they just brought it back (at least at some restaurants) last month; it had most recently come back as an LTO in 2021
Back when I was in college (early 1980’s), Burger King had a veal parmesian sandwich on Hoagie bun. I liked it. and I wouldn’t mind eating it again.
15 years ago I used to get a DQ Flamethrower and onion rings once a week. I see it’s still on the menu but my local DQ closed. Does anyone know if they’re still good? I’d take a road trip to get one.
I would love for Wendy’s to bring back the Chipotle Caesar salad, the dressing was so amazing. I’ve tried other similar types of salad, most recently Panera’s version of a Southwest Caesar, and nothing comes close to it. It was on the menu for a couple of years in the early 2000s , I was doing Atkins and ate that salad every work day and never stopped enjoying it.
I’d like McDonald’s to bring back the old chocolate shakes. The shakes they make now are soft serve with chocolate syrup mixed in. There’s a chemical taste to them. YUCK-O. There used to be a dedicated machine for shakes. I also miss the twist cones - chocolate and vanilla twisted together. 
There are a lot of good ones here, Taco Bell’s Chilito and 7 layer burrito (that one hurt).
Not sure if anyone has Taco Johns but they had a dessert called the Apple Grande that was essentially a deep fried soft taco shell laid flat with hot apple pie filling spread out, crushed candy red-hots and cinnamon, topped with shredded and melted Mexican cheese blend.
Not exactly an item, but I sure used to pig out on the Wendy’s Super Bar! It provided excellent calorie per dollar value for a cash-strapped bachelor in his twenties, especially with a coupon from the weekly junk mail.
That’s the only thing I would back to McDonalds. Their food is disgusting but those nuggets were good.
I could swear that when they first tried them in the 70’s they were called “Golden Nuggets” but I couldn’t find anything on that.
The cheese chilito was my favorite, by far. I don’t think any competitor at that time or since has been able to offer an equivalent item.
There was a time when Arby’s ran ads with the slogan, “ARBY’S - America’s Roast Beef, Yes Sir!”
Hardee’s, that’s what they’re called around here, back in 2015-16 had what they called a “Natural Burger.” It’s really just a really good hamburger. I used to love those. I think that’s the only fast-food burger I ever loved.
On the west coast, Hardee’s is Carl’s Jr. They also had the natural burger and it was really good!
…Which are now discontinued as well! 
Tim’s used to have mini-apple strudels. A couple were perfect for a late afternoon coffee. Alas, I must have been the only one in Canada who liked them.