I have a fetish for Burroughs and Kerouac I have to admit.
I love the psychadelic trippiness of Burroughs, the way he create Hieronymus Bosch like landscapes in the mind, and of course is often macabre and very funny sense of humour which is akin to the Bukowski anti-hero in a lot of ways. Whenever I read Burroughs I always experience vivid dreams, seriously, like it dredges up the silt in my unconscious in some way. He acts on me internally.
Kerouac has the opposite effect, he just chills me out, and reminds me that the world is still a very big physical space with many roads still left to try.
Vonnegut's Mother Night and Slaughterhouse 5 have always been favourites, as have Hamsun, Celine, Robert Anton-Wilson, Henry Miller, Francis Stuart and Houellebecq's novels.
A young writer I adore who is in the very same vein as Buk, but writing from a UK perspective is Niall Griffiths.
His novels are very dark, the characters often being young unemployed drifters in a small seaside community, giving first person accounts of their day to day alienation and resistance to a cold and impersonal world. A bit bleak often, but very funny too.
Griffith writes about nature in tooth and claw in a beautiful way too, hinting at the animal that lurks in all of us beneath the most civilized veneer.