Weirdly, I've given this problem some thought.

I like to go for famous people with memorable delivery styles and as much variety as possible:

• Ed Wynn
• John Wayne
• Bob Hope
• John Fielder
• Noel Fielding
• Kumail Nanjiani
• Peter Capaldi
• Richard Ayoade
• Stephen Fry
• Steve Buscemi
• Peter Cullen
• Jonathan Frakes

This is also a useful reference group for ad-hoc NPCs when running a game of Pathfinder.

Edit: I focused on male voices, since we're talking about doing the Hobbit. But now I want to reuse this for NPCs.

Some great, distinct, female voices:

• Reba McIntyre
• Jane Krakowski (30 Rock, Unbreakable Kimmy Schmidt)
• Natasha Fatale (from Rocky and Bullwinkle) (June Foray)
• Granny (from Luney Tunes) (June Foray, Tress MacNeille)
• Jane Kangaroo (Horton Hears a Who) (still June Foray)
• Daisy Duck (often Tress MacNeille)
• Dot Warner (Tress MacNeille again)
• Mrs Featherby (DuckTales) (Tress MacNeille again)