Thanks Sander.

It is at least partly illuminating that there is a difference between what is popular and what is considered educational, and that what is popular can be quantified. I am not sure exactly what it means though. A few possibilities:

1) the functions that are useful for thinking computationally are different from what gets used to get things done or

2) some functions are common because they are utilitarian or plainly mathematical or

3) it could just be that my point of view represents a small minority of users.

Great list and a nice idea!

I would've chosen With rather than WordList, as it is more commonly used. But we can automate this process to choose the most 'popular' functions:

wlf=WolframLanguageData[];
data=WolframLanguageData[wlf,{"Ranks","Name"}];
sections=data[[1,1,All,1]];
results=Table[
    tmp=Select[DeleteMissing[data,1,\[Infinity]],Not[StringStartsQ[#[[2]],"$"]]&];
    tmp[[All,1]]=(m/.#)&/@tmp[[All,1]];
    Last@*First@*TakeSmallestBy[First,1]/@SortBy[GatherBy[tmp,StringTake[#[[2]],1]&],Last@*First]
,
    {m,sections}
];

And showing the results:

TableForm[Transpose[results], TableHeadings -> {CharacterRange["a", "z"], sections}]