I've probably never worked harder on a project than on RTX at LucasArts. For a while I did a long series of 90-120 hr work weeks. Unfortunately, this didn't result in a great game, but in the end I learned an enormous amount on my second professional game project. Lead programmer Eric Johnston had enough faith in me to give me ownership over the AI and visual FX systems for the entire game. While in retrospect, this was way more work than 1 engineer probably should tackle on his own, it was really quite fun and educational, and I'm grateful that Eric allowed me to tackle it.
It's also nice that despite a scathing review, Gamespot took a sentence to call out a positive note on my work:
"... to their credit, the enemies in the game are pretty good about taking cover when coming under fire" -- Gamespot 2003