As should everyone - seriously!
Nilp - you have to take into account his alter-egos. So while he sounds reasonably normal Adam sounds like my old teacher because he puts Nilp down all the time and Alice, well Alice has quite a low and melodic voice to me.
Eomer - has never actually sounded Scottish though I've always known he is. He just always sounds like he's laughing.
TGWBS - sounds rather excitable and sometimes a little like Gollum.