Off the top of my head when it comes to the genres I read the most:
-The Girl with the Dragon Tattoo. The nordic thriller genre was highly prolific well before it, at least since the 1960s, but Larsson popularised it to a wider non-Nordic public by introducing cartoonish, exaggerated, violent, movie-like elements that contrasted with the tradition both of Nordic thrillers and of crime novels in general, and formed the basis for many successful writers that came afterwards.
-Battle Royale. Pulp, extreme and theatrical, it is a landmark of dystopian fiction that IMHO deserves to be in the same realm as 1984 and Lord of the Flies (not necessarily in prose quality, but part of it is because it’s not in English originally and the translation is bad) and is perhaps the single most important work of the whole “killing game” sub-genre.
House of Leaves by Danielewski is one for me. I also loved Lincoln in the Bardot by George Saunders. Annihilation was also excellent. Bluets by Maggie Nelson is beautiful, though it isn’t fiction. I’ve started reading Infinite Jest by David Foster Wallace and it’s fantastic so far.