This. ^^^^
I use, in a non-stick pan.
[ul]
[li]Tortillas. [/li][li]Fresh salsa. [/li][li]Shredded cheese. ETA, just a standard “Mexican” blend. I find cheddar isn’t quite right, and jack isn’t quite right either. The mix is nice. [/li][/ul]
Warm, flip, serve when cheese is melted and outside of tortillas is toasty.
Serve with guac and/or sour cream, if you like.
I really think it needs just a smidge of butter, even on one side, to push it over from good to really good when you throw it in the pan.
Buttered and grilled. It can be full size or a tortilla folded. Cheese and jalapeno are required, just about anything else optional. I prefer to serve with sour cream, guacamole, and fresh salsa on the side.
Yes.
I’m with Alton Brown on the whole one-trick pony kitchen appliances. They’re just not necessary the large majority of the time. Only a couple of exceptions come to mind - popcorn popper, and coffee maker - though depending on the maker, it can be argued that it could be used for other things!
I like to do them on my old-fashioned round waffle iron, but I never close the lid. Flour tortilla, a few Southwestern precooked chicken strips (from Aldi), shredded cheese, another tortilla on top. As the cheese melts, press the top tortilla down around the perimeter to get something of a seal. Finally, flip it to get those nice Maillard reactions on the other side as well.
Cheese, fresh roasted green chile, and a scrambled egg.
When I make popcorn, I use a pot on the stove. No need for a uni-tasker. Although next time I might use a Pyrex bowl in the microwave oven, as suggested in a thread I read here this year.
I seldom make quesadillas. I do like to make sincronizadas with refried beans, ham, and cheddar; topped off with guacamole, sour cream, shredded cheese, and diced tomato.
I fixed quesadillas for lunch. Smear refried beans on a tortilla; place bean-side up in a skillet; cover beans with cheese (Colby-Jack for us); top with another tortilla. Flip when bottom tortilla is toasty; toast the other side. Put on a plate, and cut into quarters. Eat. 
Fwiw, the kids don’t care for the beans. They’ll eat just cheese quesadillas.
Add ham, and you have a sincronizada. 
Best popcorn popper in the world is a big wok with a lid.
To me, a quesadilla is just two tortillas with cheese, toasted in a frying pan or griddle. I don’t even use butter or oil, though my wife likes how that affects the texture. (It’s a grilled cheese sandwich with tortillas instead of bread.)
It doesn’t require anything else, in my opinion, but I do often put a little guacamole, salsa or hot sauce on after it’s cooked. My wife likes to add sour cream.
I honestly don’t care for any other ingredients. If I wanted meat, beans, vegetables, etc. then what I really wanted is better called a taco, nacho, burrito or enchilada.
I heat my tortillas directly on the stove burner first using tongs, then fill, then melt in a non-stick pan. No butter. But you need to fire the tortillas before filling so they won’t be all gooey and doughy. I use the Mexican cheese blend from the grocery store and a sprinkling of cojita cheese, too. Guacamole makes a nice dip.
Try again but this time with peanut oil. And bread it with panko crumbs.
Shh. Don’t tell my husband. I don’t want any more steps.
How about a breakfast quesadilla?
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[li]Heat a 9" non-stick pan with a teaspoon of oil to medium. Add a beaten egg, when bottom starts to set, sprinkle with cheese and place a corn tortilla on top.[/li][li]Let egg cook a bit more and using a broad thin spatula, *flip.[/li][li]Sprinkle with cheese and add another tortilla.[/li][li]Flip once more to crisp each tortilla and serve with your favorite salsa.[/li][/ol]
Optionally, add bacon crumbles with cheese.
OI! MR. May20! Ask for ham!
But a sincronizada uses corn tortillas. With wheat tortillas it’s just a quesadilla with ham.
And the ones I’ve gotten off of taco trucks (in L.A. and Orange Counties) use flour tortillas.
In Mexico (which is the only place I’ve had them) they are made with corn tortillas. Thrillist backs me up on this. Typical gringos - using wheat when corn is better. 
It’s very complicated, don’t try it at home unless there is an adult there to help you!