Like Mike, some of mine are better told in private.
But certainly first solo. Weird that I can't really remember much about the airplane or the day, but I certainly remember the feeling of "holy f'ing poop, I'm up here by my lonesome". Hard to describe, but I'm sure it's very much the same for all of us. I could also pick my primary instructor out of a lineup of short pudgy Italianish dudes with 100% accuracy, even 20 years later, although I think he left shortly after my solo.
In no particular order:
Flying back from my commercial ride down at KBWG. Got as high as the poor Gutless could manage. Perfect night, no moon, solid undercast, seemed like you could see the entire Milky Way.
CFI Oral is burned in to my unconscious. I will be an effing expert on "center of lift" for the rest of time. Once bitten, you know.
Couple of "oh, so this is what the inside of a thunderstorm looks like" moments from freight. Apparently if the dirt of decades is coming off the floor and hovering around you, you've now "got the patch". I only learned this later!
Some incredibly fun times with fellow pilots at FLX. You (or I, anyway) don't realize how much fun you're all having until it's 10 years later and you've got to go to Work, and you kind of don't want to.
Landing in a tropical storm at KPNS. Taxied in all proud of myself and the DHL guys refused to come out and unload the airplane because "it's crazy out there".
A certain night in KPBI with my F/O and another crew, which probably should be erased from my memory, in case it becomes downloadable in the future.
Coaxing the poor Bitchjet up to "Four-Five-Oh, dude!" to get over a line that stretched from Ohio to Louisiana. The lightning strikes were constant. It looked like a freaking rave, or maybe a constant barrage of cluster-bombs. Very much a "oh, Little Man, you think you Know Something?" moment.
Doing the dreaded single-engine approach in to KTUL during my MU-2 training. Got a little low and slow (purely due to being insufficiently wary and skilled, no fault of the airplane) and the unbelievably salty old badass in the other seat who ate nails for breakfast was like "Ok, maybe I should..." "No, I got this". And I did. That may be the
proudest moment. Although I doubt I could do it again.
Flying up the Outer Banks of NC with a high school friend back in the mists of time. Literally running from the ramp to the ocean (all of maybe 300 yards) and camping on the terrestrial-vehicle-prohibited beach all by ourselves (and in contravention to Park Service Policy, I think). Waking up, looking down the beach and seeing not another footprint, let alone a human being as far as the eye could see, with the tide way out and thunderstorms on the horizon.
Landing the Mitsi in Nowhere, Nebraska in the dark winter to pick some electrical conduits. Hit reverse..."WHOMPH"...can't see a damned thing, snow everywhere. The semi showed up like a ship out of the fog 30 minutes later. I don't think I said three words to the driver, nor him to me, and I'm pretty sure we were the only breathing human beings for 30 miles around.
Once again, obviously the first student solo. Far more nervous than I ever was when it was my dumb ass in the seat.
My first (and hopefully only) experience with tailplane icing leading to an incipient tailplane stall.
The first time I flew a jet in to Aspen at mins as PIC. Another one of those "Wow, I did that, I'm awesome!" moments where...nobody else is even marginally impressed. "So, are you guys going to take some fuel, or what? There's a good game on".
I could go on. And on. You get the idea.
For all of its faults, this crap doesn't lack for Memorable Moments, does it?