George RR Martin's A Song of Ice and Fire - A Storm of Swords is my favorite, simply because of the emotions that it causes me to feel; hatred, sorrow, pity, and elation all in one book. Simply fantastic.
Robin Hobb's Royal Assassin, Book 2 of the Farseer Trilogy, simply causes me to feel constant pain for the main character. The fact that she can evoke such feelings within me is simply astounding.
Steven Erikson's Memories of Ice, Book 3 of the Malazan Series, is breathtaking in scope, mythology, and emotional impact. The battle scenes, the personal struggles, and the godlike ascendants weave together in a complex story full of pathos, bloody conflict, and some of the most fantastic battle scenes I've ever read. Great book.
China Mieville's Perdido Street Station evokes a lot of things in me: wonder, fear, disgust, and shock. Mieville manages to create one of the most disgustingly real cities ever in New Crobuzon and the way in which he weaves the storylines together is very satisfying. The creatures that he inhabits the world with are strange and (usually) really cool. Kinda overblown prose at times and he cannot write battle scenes, but I really enjoyed his books so far.