You could always go with Macallan 18yr. It is a very smooth, delicately sweet whisky. I would expect anyone who likes Glenlivet 12 to absolutely love Mac18.
It is also expensive, notoriously so, and therefore has a certain luxuriousness to the gift. While I have found others that are as good and cheaper (Aberlour 18yr) they don't have the same cache as Mac18.