Now You See, Me Now You Don't v. Up, Up, and Away

If I were in a classroom environment where I was charged with teaching people how to argue, I would start here, I think.

Invisibility v. Flight
You get one of these superpowers. Pick one. Quick, pick one, no thinking. Now, write down the reasons you picked this one.
This is the gut reaction part. We would use this part to talk about how people often have opinions before they think through their reasons, but there are reasons buried in the heads of those people. This is the part where I get the students to realize that opinions and even guesses don't come out of nowhere, and that they can be unearthed with a little work. (Then we do a little work to unearth our reasons for our gut decisions, our choice of invisibility v. flight.)
Let's listen to some other people make this decision: This American Life's "Superpowers" Episode.
Act One of this epidsode is thirteen minutes of people choosing invisibility or flight. This is the part where we listen to how other people think through choices. Students would write down all the reasons they hear and make note of reasons they did not think of and any reasons they would choose for themselves after hearing them on the show.
Now, think of reasons why someone would pick the other superpower. Not the one you picked. The other one.
This is the part where we think of The Other Side, where we learn to think through the opinions of others, even if we don't agree with them. Students have to come up with reasons for the other power (at this point, some could be waffling on their original choice, but I would simply have them examine the one they didn't go to on their gut instincts).
Taking all of this into account, now you get to make a new choice. Invisibility or flight? You also get to come up with intelligent reasons for your choice. That will turn into a fun-yet-intelligent essay.
This is the part where they work on producing a piece of writing based on all this thinking. We'd probably work on outlining and revising and proofreading, but the basic idea of all this is that Invisibility v. Flight is not a supercomplex issue for them to deal with, but a simple choice that turns into a more complex and mature thought process.

We could also:
-have a class debate
-look at the benefits of both superpowers in actual comic books (in the lives of "real" superheros) -imagine the drawbacks of each power in everyday life (outside the lives of superheros)
-imagine the benefits of each power to a regular, non-hero-type person
-establish rules for each power (what would and would not turn invisible with you, how fast and high you could fly, etc.)
-move on to discussing something a little weightier like the agreeing or disagreeing with the claim that begins F. Scott Fitzgerald's essay "The Crack-Up": "Of course all life is a process of breaking down..."