I think it was either Beyond Good and Evil or Guilty Gear Iruca for PC. And then there were psychonauts and Megaman X8, I think all of the were worth it. Guilty Gear Iruca might have been the weakest in the series for me but I had a lot of fun with it too, and it got me to try X2 later.

And the Megaman game was actually my favourite in the series, I liked having lower difficulty with Axel and replayed it a few times, I was surprised to discover that the difficulty changed the ending on my second playthrough. That was such a great time in gaming.