Hi,
As part of their IEG [1], Eran and Ravid have mapped the gadget use in all wm projects https://meta.wikimedia.org/wiki/Gadgets
It gives a good overview of gadget popularity and may help to discover hidden gems.
Cheers, Micru
[1] http://blog.wikimedia.org/2014/04/22/visualeditor-gadgets/
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