1) vertex/face snapping: Being able to either select a Vertex/face on an object then snap to another object's vertex/face or once activated just snap any vertex/face to another object.

There are many use cases for this like, Prim snapping, modular parts for structures, road, path, walls and fence sets, could even be used for clothing and wearables on avatars.

2) Pivot snapping: Being able to move the (translation gizmo) pivot point to any vertex on an object, this would be useful for adjusting anything that rotates in XYZ, like a door or window.

These two features could be part of a snapping tool set.