I'd pull out a phone book, pick a name at random, and write, "Fuck you John Doe. You know why." I like to keep them guessing.
My favorite epitaph is Mel Blanc, the guy who voiced Bugs Bunny, Porky Pig, Yosemite Sam, and a bunch of other Loony Toons. "That's all folks!"
Rodney Dangerfield's epitaph is also fantastic: "There Goes The Neighbourhood". As for me, most likely cremated, or fired out of a cannon into space... I'd probably not have a gravestone or anything like that.
I'd also like to rig my body so at the funeral home I pop up out of the coffin like Big Mouth Billy Bass and start singing "Rock you like a hurricane".
"I see dead people." As for my funeral, I'm going to eulogize myself via a prerecorded video that will eventually make it's way to YouTube. When my 15 minutes come, I won't be around to enjoy them. I also want an open casket wake, and I want to be dressed as Bozo the Clown.
I would like something referential yet confusing to those who don't get the reference. Like: "These pretzels are making me thirsty" Also, no wake, no funeral. Whatever salvageable organs, body parts, etc. donated to someone/something, followed by a cremation. Hopefully I will have lived a life to where my loved ones will throw a huge party afterwards. See you in hell motherfuckers.