It doesn't have to be the hardest Boss Fight, just the one that is most memorable to you personally.
I'd like to say that my favorite boss fight for its innovation and general wtf-factor has to be Psycho-Mantis. I know I might be picking the easy one (and simultaneously ninja-ing quite a few of you) but MGS's resident telepathic nutjob was one of the most unique fight's I'd ever encountered. Maybe even the first 4th wall breaking fight... With all the video output changes, the controller movement (which was really neat at the time) and the "secret" to beating him. A well scripted boss encounter that I'll take with me to the end of my days... or at least until senility or Alzheimer's claims it.
Honorable mentions:
The End - MGS3
Kefka - FF6 (For being such a persistant ASS)
I'd like to say that my favorite boss fight for its innovation and general wtf-factor has to be Psycho-Mantis. I know I might be picking the easy one (and simultaneously ninja-ing quite a few of you) but MGS's resident telepathic nutjob was one of the most unique fight's I'd ever encountered. Maybe even the first 4th wall breaking fight... With all the video output changes, the controller movement (which was really neat at the time) and the "secret" to beating him. A well scripted boss encounter that I'll take with me to the end of my days... or at least until senility or Alzheimer's claims it.
Honorable mentions:
The End - MGS3
Kefka - FF6 (For being such a persistant ASS)