My once in a lifetime moments...hmmmm.
Having a photo with Nigel Benn (once middle-weight world boxing champ) as he was 'punching' me

Shaking hands with Prince Charles
Meeting Charlton Heston and getting his autobiography autographed. My favourite actor, he was playing on stage in London opposite his wife Lydia about a decade or more ago.
Being chased through the worst streets in San Francisco by a crazy homeless guy
Snogging my then girlfriend in the middle of a torrential downpour and thunderstorm in a completely deserted Trafalgar Square with Big Ben chiming midnight.
Saving a man's life.
Flying a kite for the first time on a mountaintop near Rouen in Normandy, maybe two decades ago. Loved them since then.
Watching the sun rise from the top of Masada.
Played Magic: The Gathering a bit many years ago. Won a game with 6 players with my cool blue/black deck. Wiped out five players in the one turn with various Time Warp/Ancestral Recall type tomfoolery. Haven't really played since then.
Game related: Wanting to get the best ending possible in SFII Turbo back in the day, I tried and tried and tried and eventually managed it. Using Ken, beat the game on hardest difficulty without losing any rounds. Only difference as it turned out, was Chun Li at the very end doing her "yah ta" sound. :-\
Game related: Thoroughly dominating for a series of games in AvP2 and getting accused of cheating (Go PredAlien!).