Just to be annoying.
Poached eggs and toast
We’ve almost always have around pre-browned ground beef and/or unsauced shredded pork portioned out and frozen.
Mix a jar of salsa, a jar of queso sauce (I usually have both on the shelf), stir in cooked ground beef or pork. Heat on the stove. Top with shredded cheese of your choice. Eat by dipping nachos or corn chips into it. Add a salad.
Not terribly healthy, but filling and warming and fast, when I don’t feel like cooking anything more complex.
A pound of pasta, boiled, with a jar of spaghetti sauce. My parents would be horrified–no protein! No green vegetable!–but my husband was raised by a woman who would literally fix a box of instant potato buds for dinner, so he doesn’t mind.
Breakfast for dinner is popular here too if something’s needed in a hurry. I usually have bacon around, or sausage, and there’s bread for toast, or I can make Bisquick pancakes, and of course eggs. There’s usually fruit about too.
Some sort of pasta would be the alternative - cacio e pepe, olio e aglio, alfredo, something like that.
I can do creamed tuna on toast in about six minutes flat, including toasting the bread.
But I’ve got a whole range of other options in the pantry or freezer most of the time: canned chili, taquitos, canned chicken on rice, tuna on mac & cheese, precooked pulled pork, frozen Chinese.
Pseudo-pan-ethnic pizza. I pretty much always have pita in the freezer. Spread with ajvar, top with cheese, maybe a minced pepper or something if I’m feeling fancy, some kind of cheese, pop in the toaster oven. Possibly topped with a crispy fried egg and some smoked paprika or some other herb mixture from a shaker Penzey’s Fox Point is my usual fave.
When I lived a block and a half from a Mexican grocery, quesadillas were more frequent: corn tortillas, canned refried black beans, cheese, any bits of leftover veggies or maybe shredded chicken in the fridge, salsa, cilantro.
With some of the Italian food, you have to also be careful you don’t run out of vowels. 
Three eggs
Whatever cheese I have around
Hot sauce
Flour tortillas
Fried egg tacos!!!
Lots have mentioned omelets and baked potatoes were mentioned above. I do “chip omelets”. I nuke the potato in the microwave, then cut it up in small cubes after it’s cooked (make it a bit rough to go brown), then fry it in a frypan and make the omelet and have the chips on the omelet.
I also like baked potatoes with baked beans or a spud with some (lots) butter and one of those flavoured tins of tuna, lemon pepper or sweet chili or something.
Another easy and quick thing is cooked pasta with a little tin of evaporated milk on it. You can put other stuff in if you want, like peas or something. Or just pasta with olive oil and cheese.
To all that said Tacos… I’m with you… first choice…
A close second… and easier… a grilled cheese with a green apple in the middle and a quinoa salad… my daughters favorite too.
Or… slow cooker… put it on before you head to work… even easier.
Cheese and refried bean quesadillas. Or throw some frozen pot stickers on the stove.
Wife and I always keep some chicken kievs in the freezer just for this occasion - into the oven, ready in about 30 minutes, microwave a baked potato in 6 minutes, heat up a can of peas & carrots. Done.
Boxed Macaroni and Cheese with a can of tuna and a can of mixed veges is my go-to.
Runner up is chips, canned refried black beans, cheese, and salsa. Add sour cream if you want to be fancy.
Spaghetti. We’ve always got pound packages of hamburger in the freezer, spaghetti sauce and spaghetti in the pantry.
Or maybe manwiches if we have hamburger buns. There’s always a can in the pantry too.
Chili mac rounds out the short list.
Can throw any of those together in under 30 minutes.
Depending on what I want, a can of soup, a frozen pizza, or if I don’t want either, fried egg sandwiches. 2 or 3 eggs on toasted wheat bread, with some locally-produced stone-ground mustard. MMMMMMM!
A couple of fried hot dogs and a can of doctored up Bush’s beans.
Mostly premade stuff, either frozen meals or these fairly cheap shelf-meals.
But, for actual prep, eggs and other breakfast food are the common choice around here. Or, if you can count toasted bread, then tuna or chicken salad are nice. We used to do quesadillas a lot, though now it’s mostly nachos or grilled cheese instead. My mother is really into microwave-baked potatoes–especially if you add some meat like bacon bits or a some lunch meat to them. Oh, and we can add rice to anything, since it’s quick. I also sometimes use instant potatoes.
Oh, and one thing I used to do but not as much anymore: a can of mixed veggies with some soy sauce, plus some cooked meat. I could put a bit of chicken in the microwave for 10 minutes, or grab some beef crumbles, or throw in some canned chicken. I think I even once used a fairly light tuna. It doesn’t matter much, as it’s the veggie broth plus the soy sauce that gives it flavor.
Lean meat in a skillet with olive oil
Toast pita or naan lightly in pan
add hummus and vegetables.
eat it like a gyro or doner kebab
10 minutes.