Bobby Fischer Memorial, Round 5: The dagger on d6
For me this was the last game of the tournament (I took a bye in Round 6), and I'm very proud of how I played it. My opponent played the Nimzowitsch Defense, an opening I'd never faced in a tournament before, but I managed to grab space, gain easy development, and cement my advantage with a well-timed pawn thrust.
This win put the capstone on what for me was a triumphant return to tournament chess after fifteen years away from the game. My rating, presumably made provisional again after my long absence, shot up a whopping 128 points; I got my first-ever tournament win against an 1800, beat two strong 1700s, and finished with the same score (3.5/6) as the two guys who beat me. I had been nervous about my lack of opening knowledge, but I made it through five different openings (a closed Sicilian, a Catalan, a Bishop's Opening, an Alekhine, and the Nimzowitsch Defense in this game) with fairly good results.