See I would go for Corkscrew as it was, after all, my first "real" rollercoaster. I still remember the absolute thrill I had going on it the first time as a wide-eyed seven-year-old. However, the ride had reached the end of it's life and it was being run on sentimentality rather than efficiency. I think it was a fair decision letting it go. I must say though that I miss Ug Land like a lot of people here, and it was a shame that along with Corkscrew, the area theming had to go too.
If I had to say one, I would go for either Black Hole or Energizer.