https://www.boredpanda.com/funny-to...oogle&utm_medium=organic&utm_campaign=organic I particularly like "If you can read this you're standing on my boobs." So what's going on your gravestone? I'm thinking of: "On the whole I've found people to be disappointing"
Hodie mihi cras tibi is rather poignant but very true. A warning to the living to make the most of every day. Groucho Marx's last reported words were 'this is no way to live'.
Thought of a better one: "Some say I wasn't the sharpest tool in the box, but when you need to bang a nail in sometimes a scalpel just won't cut it."