I have a lot of favorites across a lot of genres, but I'm feeling metal tonight, so here goes:
Strapping Young Lad - City: I've had people who absolutely hate grindcore come up and tell me how much they love this album. It's unbridled, tongue-in-cheek speed metal fury with a healthy dose of industrial to ramp up the intensity more than a few notches. Its follow-up, "SYL," is just as good but this one gets the nod because it came first, I guess
Metallica - Master of Puppets: This, to me, is the greatest heavy metal album ever recorded. So much melody, complexity, and innovation on this album it's just plain sick. 'Nuff said.
Tony MacAlpine - Maximum Security: After Yngwie got big, neoclassical shred albums were a dime a dozen, but this one, despite being the same style more or less, is better than anything Malmsteen has ever done. Tony's amazing dexterity and technical ability almost mask his incredible sense of melody and taste. Truly one of the most underappreciated guitarists of his time.
Dimmu Borgir - Death Cult Armageddon: Some diehards prefer their black metal stripped down and rough as a rock quarry, but this new brand of slick, tightly played, and epic-sounding black metal works for me just fine, and it's never been done better than on this album.
Angra - Rebirth: The boys from Brazil are the best power metal band working today. So many other groups tend to follow the same neoclassical, double-bass-driven formula, but Angra's albums are always so full of surprises and unique twists. Though Rebirth is not particularly innovative compared to their previous work, I consider it their best because it more or less perfects the style they'd been working for so long.
And it wouldn't be a favorites list without....
Ocean Machine - Biomech: This is the single greatest album I've ever heard, and I can still say that after hearing it for the first time some six years ago. Even though Devin Townsend had released some absolutely stellar albums before and after Biomech, nothing he's ever done quite lives up to it. Everyone should at least give it a try.