Once IIA is relaxed to a sane axiom [read: abolished almost entirely], there are multiple methods that work like versions of STV. Besides, Arrow never applied to ordinal voting methods like Approval (which is OK) or Range (which I strongly dislike for other reasons).
Another economic topic would perhaps be marginalism, so we don't keep getting flooded with "but why is water cheaper than diamonds, it must be injustice/bad values/conspiracy".
And perhaps some kind of history of thought on value, so we don't get the simple version of labour theory, or the Fisher-Price version of utility theory again and again.
Perhaps I sound like a snob, but I find a lot of economic discussions are derailed by having to clear up confusions that appear repeatedly.
The fact that it holds when there are three or more options but not for two options just doesn't sit right with me.
See the Gibbard-Satterthwaite theorem.
Pretty much the only scheme that avoids this is "choose a voter at random and elect the candidate they like best".
Which isn't a very important consideration compared to other attributes of election methods. Usually, coordination and signalling problems make tactical voting inadvisable. But even when tactical voting does work, it's not necessarily a problem.
The source of all of Arrow's nonsense is treating an election as a very large opinion poll on a single candidate. Of course pollsters hate liars, so everyone who takes Arrow seriously tries to eliminate tactical voting.
However, that's the completely wrong model. An election is an opportunity for a citizen to use their equal political weight to try to steer the polity. If some citizens managed to be smart and use their political weight smartly good for them. So what if their vote wasn't their true preference?
Tactical voting is only a problem when the election method allows a minority to win frequently - because political weight isn't really equal in that case - but one can imagine methods where tactical voting can happen yet the winning candidate always ends up with a majority (e.g. France's 2-stage Presidential elections). In those cases, tactical voting is not a problem to be eliminated.
And at this point we learn how many people's true preference is to vote themselves as president!