Anata - "The Conductor's Departure".
Totally unique technical Death Metal from sweden. What they bring, is a sense of melody and harmony you don't normally see in this genre. To me, they are masters of contrasting "pretty" and semi-jazzy melodies with the standard DM ugly tonalities, just listen to "Entropy Within" off their Myspace. The music ridiculously catchy as well, such as the downright beautiful outro riff of "Renunciation". Holy shit!
Yes - "Close To The Edge"
Fucking. Masterpiece.
I love love love love this record!
Atheist - "Unquestionable Presence"
Not much to say here, really. Some of the earliest true technical Metal put out, and still some of absolute best.
The heaviness also makes me wonder why I ever bothered detuning my guitars. These dudes play in E, and stuff like the intro to "Enthralled In Essence" is heavy as life.