Three favorites, all (long) day hikes:
Up Huntington Ravine, down Glen Boulder. Only problem is that I usually hike alone and I'm getting too old to do that by myself without my family going nuts.
Up Nelson Crag, down Boott Spur or Glen Boulder. In my opinion, the best way up if you prefer seeing a minimum of other hikers.
From Pinkham to the Great Gulf via Jackson Road, etc., up the headwall, and back down to Pinkham via whichever route is likely to have the fewest people so that my groans from crunched knees aren't broadcast to the world.