These are a few albums that I did not really get on the first listen or so, but gradually grew on me.
ULCERATE: THE DESTROYERS OF ALL
It did not take me much to get really into this album, but it did take one or two listens before it really started to make sense. Ulcerate is a band that combines brutal death metal and post-metal into something almost otherworldly. It is very clear that the band's background is in brutal death and that influence shines through in the drumming, but the riffs are chaotic and dissonant, almost freely forming with very little structure. It's like Isis meeting Origin.
REVOCATION: CHAOS OF FORMS
The thrash metal album of the year came from an unlikely place, one of the very best retro thrash metal bands that has formed in the last few years. Revocation really found their sound on this one. Even though I have liked their material in the past, this one blew that away. However, the first few listens were not terribly impressive and it took me some time to realize how fresh and exciting this album really is.