Back then I had a choice between Mario Kart: Double Dash and Mario Party 5. I chose the latter.
Not locking my door when I left my house only to get My Dreamcast stolen.
Not joining the Pokemon crowd when it was its peak, I would have bought tons of merchandise.
Not putting much time into my console games as I do with my handheld games, I don't know why. >_<
Not playing Wii fit / Animal Crossing: City folks as much.