Blender Git Commit Log

Additive snap for Transform. Easy snapping between two vertices, in the middle of three faces, ...

A to add the current snapping point to the list
Alt-A to remove the last one

The resulting snapping point is the average of all snap points in the list (and the one under the mouse pointer, if valid).

Snapping between two verts is a matter of moving over the first, pressing A, moving over the other, confirming transform.