Cryptic - John Larkin, John Poplish. John Woodgate (rarely present in guru mode)?
John Jardine might be a candidate, but if he is a guru it isn't in an area I know much about.
John Fields might be a guru to the 555 users' community - a very low-rent district.
My vote goes to Win Hill - he knows what he is doing and and can spell out why he does things the way he does.