I don't know if I could point to any
one as my stand-out favorite but some of my favorites (in no particular order and covering a wide range of experiences) are:
Being in the upper Mariposa Grove late in the afternoon as the sun is starting to melt away. Not a single other human anywhere in sight (or earshot). That's when I knew that this is where I want my ashes scattered.
Standing by the railing at the top of Nevada Fall (late spring after a heavy winter so the water was raging), staring so intently in to the water that everything else just melted away. Like staring in to the face of God (and I'm not even a particular believer!).
Sunrise at Glacier Point...a handful of other people around but everyone being completely respectful of one another's solitude. The only thing you could hear were the birds.
The first time I came around the bend in the Upper Yose Falls trail where you get your first close-up of the upper falls...the ground literally vibrating beneath your feet with the power of the falls.
The first time I entered the Valley on the Southside Drive and that amazing view of El Cap fills your entire windshield. My jaw (quite literally) dropped open and I think I forgot to breathe for several seconds (unfortunately, like so many people, I also stopped dead in the middle of the road but at least there weren't too many other people around). This view can still move me to tears just thinking about it.
Pretty much every time I log miles on one of the old roads...especially if it's a section I've never done before and even more so if it's obviously a section that very few (if any) people have done in a very long time. This is especially gratifying when you've got a view in to the Valley of wall-to-wall cars and you haven't seen a single person on your entire hike.
The first time I met Tom Bopp at the Hotel Wawona...his warmth, wit and depth of knowledge on things both musical and Yosemite-historical ensure that I pay him at least one visit every time we're in the park.
Hell, it really boils down to the fact that just about every single day I spend in the Park adds to my list of favorite moments!