"The Real Me" by John Entwistle The Who
"Lemon Song" John Paul Jones Led Zep (already mentioned)
"Helter Skelter" Paul McCartney Beatles
These bass lines do more than just "thump the beat in time", any asshole can do that. Those basslines are played like "Lead Guitar", they actually create a melody and "drive" the song.
I seriously don't know who's better, McCartney or Entwistle.