Entwistle - from "Live at Leeds" era through the Alembic/Sunn period.
Geezer - especially "Bassically/NIB," not very good tone currently sad to say.
Jack Bruce - mostly the big fuzzy bass of old, but still the best sound I've ever heard Warwicks and/or Hartke heads make.
John Paul Jones, Chris Squire - these guys have always sounded great, with both have had different tones, basses, and rigs over the years (and sometimes just from song to song) but always excellent tone.