"Finally, some help, bumpty-bumpty-bump! Here I was, just minding my own business, trying to make the big boom, big boom, bumpty-bump, when all of a sudden war breaks out! War, bumpty-bumpty-bump! Those pirates, they went away, but on the way out of the cove they sank the ship that was bringing me my gunpowder! I need it! I need it for the big big boom, bumpty-bump!
Anyway, I tried going down to Sonofa Beach to see if any of it washed up, bumpty-bump, but those lobsterfrogmen down there are too tough for me to handle.
You -- you go get it for me, bumpty-bumpty-bump? 5 barrels, at least."
"My gunpowder! Big boom! Big big boom! Thank you, bumpty-bumpty-bump! Bumpty-bump!"
He gazes at you thoughtfully for a few seconds, then a smile lights up his face and he says "My life... er... my bombs for you. My bombs for you, bumpty-bumpty-bump!"
The Lighthouse Keeper's eyes light up as he sees your gunpowder.
"Big boom! Big big boom! Give me those, bumpty-bump, and I'll make you the big boom!" He takes the gunpowder into a back room, and returns with an armload of big bombs.
The lighthouse keeper is a reference to The Trashcan Man from Stephen King's The Stand. The image resembles the character as played by Matt Frewer in the film adaptation.
After completing the quest, the lighthouse keeper says, "My life... er... my bombs for you." which is probably a reference to the Zealot unit speech from the game Starcraft.