Crispy M&M’s. No longer available in the US. I found where I could order them online from Germany, but I’m worried they’d be spoiled in transit.
Suddenly S’mores, not only are they gone, no one but me even seems to remember them. FTR, I usually didn’t microwave them, but rather eat them right out of the package.
The Edge at Pizza Hut. I was a firm believer in the ‘more crust on a pizza, the better’ until this came out.
Snapple’s Cherry Lime Rickey Soda. Remember when Snapple had a million different flavors? This one didn’t survive the cut. 
Coca Cola Black. My first taste of this was wretched, but I bought it, so I was gonna drink it. By the end, I was wishing I’d bought two.
For me it is the Chocolate Cream pie from Baker’s Square/Village Inn. They still make it somewhere and it still shows up listed on the website, but they don’t sell it at any locations I have found west of the Mississippi. They had it, then discontinued selling it at any of our local stores about 10-15 years ago. Since then, they have brought it back twice. Both times I learned to get to it before 5-6 pm or they would sell out. Both times they stopped carrying it. Why? Lack of demand…
Coborn’s Delivers grocery delivery service had this great taco pasta salad back when they were called Simon Delivers. It had penne in it and this great creamy sauce, along with olives, onions, and peppers…but now it is no more.
Bishops Finger Kentish Ale. Oh, Shepherd’s Neame still brews it. They just stopped exporting it to the colonies a few years back. Bastards.
Same thing with Schweppes Bitter Orange.
Coke Black. How I miss that!
Chicago Brick ice cream–like Neapolitan, but caramel, orange sherbet, and vanilla.
Wendy’s veggie pitas: heck, all of their pita sandwiches. Also, their cole slaw from the salad bars.
Wendy’s Grilled Chicken Salad. The one from the mid-to-late 90s. It had carrots and broccoli and cauliflower in the mix. They had a great reduced calorie Italian dressing, too, and they served the salad with a warm breadstick. The presence of raw broccoli wins me over quite nicely, and the tomatoes were always arranged to be on the edges, so that I could get rid of them. Alas, they stopped carrying them sometime when I was in college, in favor of the mandarin orange chicken salad. Bleh. The only use I have for oranges in a salad is if they’re blood oranges, and then only if there are also walnuts in the salad, and the dressing is a balsamic vinaigrette, heavy on the balsamic. Not something I’m going to trust to a place that has yet to figure out decent french fries.
Bath and Body Works Iced Pineapple body splash. Though allegedly the Coconut Pineapple is similar. I’m too cheap to find out.
It’s not really discontinued, but Ulta stopped carrying Demeter fragrances, which is annoying because I liked wearing the Ginger Ale scent, but can’t bring myself to buy it online and pay shipping.
They discontinued Diet Cherry 7-Up for a while. I was pissed. Then they brought it back, and I realized how effing sweet it was. Too sweet. Sigh.
Frozen Cokes from Burger King. They have Coke Icees now, but it’s really not the same.
I yearn for those bygone products that always always filled my heart with a warm sense of family value and harmony :), including: Chase and Sanborn Coffee in little cans, Pep Vitamins, Tipalet cigars, Pitney Bowes postage meters, Bell & Howell projectorsand those playful products from Iver Johnson.
New York Seltzer - squat glass bottles, a styrofoam label to peel.
I miss the peach flavor very much…
Most recent: Marzetti’s Bistro Bleu Cheese salad dressing. Not bitey bleu, creamy goodnessy bleu. Wah.
Long ago: Pizza Hut Romano Cheese salad dressing. It had a warm deliciousness that exists no where else on the salad planet.
Flex shampoo.
Ikea’s two-foot-wide Orgel room divider lamp.
I once found an Eclipse gum flavored w/ cardamom, which I’m told tasted strongly when chewed but it totally neutralized any breath odor I can usually detect. Haven’t seen in it in 2 years.
Screaming Yellow Zonkers
Mizz Lizz Beer Bread Mix
Popeye candy cigarettes. I know they still make something vaguely similar and call them Popeye candy sticks, but they’re not the same. Not as crunchy, more fruity tasting. And no red end anymore.
Vanilly Crunch cereal. And along the same lines, vanilla Ring-Dings.
Bath and Body Works men’s after shave lotion. It was awesome. Gone.
Before you despair, check here first. You might just find that they still make what you’re looking for.
Oh, yeah, Concord Grape for me…
I remember a cleaning product called Grease Relief. It was the best for grease stains on clothing. They stopped making it in the late 90’s.