I truly wasted a few things, although not on purpose:
A bowl of fish curry (we ate three out of four) and a plate of haupia (a Hawaiian dessert made from coconut milk). I tried, but failed, to consume those things. I made the haupia for a party, but forgot to serve it. Then it turned out to be too much to eat after.
Also, two and a half hard taco shells, left over from the same party. These started out in a bowl on the counter with a bunch more, which someone ate, but these few were left behind.
I composted one tortilla that was starting to get a spot of mold, and put the rest in the refrigerator, where they should have been the entire time. Turned out I should have put them in the freezer, because when I went to eat them, they had iffy spots, so I composted all of them.
When I was baking oatmeal, I found one completely dehydrated hot dog bun in the baking supplies basket. Weird, right? You can tell it has preservatives - despite being sealed in a plastic bag, it doesn't have a bit of mold.
But I saved some things, too. We combined a bunch of leftover bits of cooked meat (two sausage patties, a hamburger patty, some taco meat) with a pound of ground beef to make what I'm calling country fried steak. We breaded it with breadcrumbs made from stale bits of bread I've been collecting in the freezer. It tasted really good, but it's hard to fault anything breaded, fried and covered in gravy.
I managed to salvage quite a bit of fruit that started to turn, including half an avocado, by adding it to smoothies. And I froze a bunch of fresh-squeezed juice we had leftover from the cocktail party into ice cube trays, which I then bagged up and put in the freezer. I've already added some pineapple cubes to smoothies, and it's nice to know we have "fresh" lemon and lime juice at hand, no juicing required. :)
For me, the most interesting part of trying to not waste food (besides reducing our grocery bill), is figuring out ways to preserve/save/use food that I previously would have thrown away. In the past, I would have never frozen juice or added a brown avocado half to a smoothie. Or combined meat bits into something else. I would have thrown it all away.
It feels better to not waste food.