Who are the most underground high-end companies

Ocellia,Wyetch Labs ,Yamamoto,Triode Corp of Japan  and to a lesser degree Coincident.

Very important answer soon.

Are you looking for a list of obscure high-end companies or high end companies that make what we think are good components and should be recognized?

For just speaker drivers and components, I would elect, among the rarest:

Goto
ALE
Cogent
G.I.P. Labs

For tube electronics (amps, DACs):

Audio Note
Kondo
Aldo D'Urso

For more sensibly priced stuff:

Synthesis (amps, dacs)
Vinnie Rossi (integrated amps with everything built in)
Lavardin (integrated amps)
LFD (integrated amps)
Trenner & Friedl (speakers)

When searching gear often the name Sugden comes up . Typically from posts from people in Europe . Audio Analogue as well