Here's what I would do:
Tie him down to the table, use max impact to knock him out so he doesn't move too much, and then I'ld use an exacto knife to make dozens of crisscrossing (but shallow) cuts over his tongue. Then I'd douse a cotton swab in acid and rub it over his tongue until the entire top layer of skin comes of. Burn all of the taste buds away down to the roots so they'd never grow back again. If I do it right, I could fulfill his fantasy -- he'd never be able to taste another thing again. Quite literally.
But I'm still not sure if I should follow through with it.
