I'll just agree with a few of yours for right now instead of coming up with my own. House of Leaves was definitely an appropriate response -- reading that at about age 16 was definitely a game changer, as I'd been thinking about trying to write along the lines that Danielewski took to an artful extreme. Of course he would outdo me again a few years later with Only Revolutions.

Around the same time, I read Ulysses. And even having read only excerpts I'd be inclined to add Finnegans Wake to the list, for I can't imagine anything being much like that book in scope or execution.

Illuminatus! Yeah. I read that one comparatively late, and Wilson's other books had rather changed my life well before I got around to any of his fiction, but this one is definitely a model for conspiracy fiction -- it's a true prototype of cultural farce, I guess, and I've read a few things from decades later that owe a lot to its ideas.

I'm also in agreement with Pale Fire as a rare book. I can't imagine fiction really ever getting better than that.

Can't think of much else to add off the top of my head, except maybe Nick Cave's first novel, And the Ass Saw the Angel. Good thread, though.