Alrighty! I was after the ultimate gross out joke that I could find, and this one rings the bell. I recall my dad telling me this one as a kid and I was dry heaving at it. I didn't even read through this as it makes me ill, lol. Just a fast cut 'n paste to put it on here.
These two guys were sitting in a bar that had a spittoon. The spittoon
was filled almost to the brim with old tobacco juice, phlegm, and other
refuse/secretions. After a few, one guy says to the other, "I'll give
you $100 if you take a sip from that spittoon." The other guy
immediately grabs the spittoon and, lifting it to his lips, takes a
healthy slug. "All right, you win," says the first guy, but his
friend keeps gulping down the goop pouring out of the spittoon.
"Please stop, you're making me sick," says the first guy, but his
friend keeps chugging the phlegm. "I can't stand it, I'll give you
another $100 if you stop!"
Finally, the spittoon is empty, and the guy puts it down and belches.
"Why didn't you stop" asks his disgusted friend? "I tried to, but it
was all one piece!"