Umineko probably has my overall favourite OST of all time.

Quote Originally Posted by Karifean View Post
One of my all-time favorites would be Golden Slaughterer.

I just love this track. It's the point where Umineko makes it clear that things aren't going to be bright and happy... ever. I could also totally imagine it playing during the fight against Ultimecia in FF VIII. The track also has several remixes that are all equally awesome.
I feel like the themes of the three witches Beatrice, Lambdadelta and Bernkastel all would make great boss themes/final boss themes actually. And all three of them are also among my absolute favourites:



Mirage Coordinator:




The Executioner:





I also really like Dead Angle:






...and Hope:





...and several others.