That final battle, right when your pupitar gets to level 55. :D I love Tyranitar...
Alas, these Gold/Silver/Crystal battles were much simpler, thats what I like most about them.
Sure, you could only have a limited amount of items, but there were enough. Back before there was competition via wireless, and you just went through your game in single player laughing at the other trainers. "MUHAHAHA I AM GOD." And then occationaly finding somebody in RL, and attaching a cord to them, and getting your butt handed to ya....
Those were the days.