Wouldn’t it be good if a “last vertex selected” option is added to the vertex merging function, in addition to " at center" and “at cursor” ? Most of the time, I would find the need to “tuck in” an extra vertex into another one and often find myself selecting a vertex, shift+S (cursor to selection), select the other vertex, shift+S (selection to cursor). I clean up by selecting all and removing doubles. It would be faster if there is a hotkey for merging vertices and the default is to merge to the last vertex selected.
Well actually I also think it is a bit annoying some times, but any way, I am not sure if this is the right place to post such requests…
I mean here it may even pass unnoticed, while if you take that request to Blender.org, you have better chances of some developer, to notice it…
Cool idea, nevertheless…