Writing one's own epitaph: that's a macabre effort that writers especially are tempted into. Thankfully, wiser heads usually prevail and more traditional chiselings usually end up on the stone.

But for whatever it's worth, here are my favorites:
H.G. Wells: "Goddamn you all, I told you so."
Dorothy Parker: "Pardon my dust."
Dorothy Parker (yeah, she was noir enough to write multiples): "Everywhere she went, including here, was against her better judgment."

And mine? (Without claiming such lofty company of course)
Just a poem, please...

Boneyard requiem
that final wormy dance
From birth to death cradle to grave
poor bastard never stood a chance.

From imbalmed flesh to forgotten dust
coffin nails long turned to rust
until...

No one living recalls his name.
He might not have ever been.