What a fun thread!
Here's my 2 cents on what's been said:
Jon Camp and Greg Lake are excellent players but, IMHO, fall into the realm of guitar players who play bass. That being said, I love Renaissance and without any lead guitar player, Jon's bass really supports the entire band. (Although he was not very good at soloing.)
+1 on Graham Maby. I've seen Joe Jackson many times and his playing is spot on every song every note. Really solid. I'm glad a lot of people threw his name out.
Someone mentioned Peter Cetera...great player...
Never knew that Alan Spenner did the bass work on Jesus Christ Superstar. There's some wonderful lines in that show although I don't know if he wrote them.
Both Glen Cornick and Jeffrey Hammond from Tull get my vote as well.
Stevie Wonder's left hand - LOL! And true! What an amazing talent!
Don't know how Jack Casady, Leland Sklar and Jack Bruce got mentioned. Most bass players know who these guys are...
Patrick O'Hearn and Tom Fowler are both amazing. A lot of Zappa's stuff is insane and they both have a solid resume of other work that is incredible.
Finally, I know that he gets mentioned here and there and, yes, falls under people who played guitar first and, yes, may not be a technical genius, but Colin Greenwood (from Radio Head) is one very tasty player.
Thanks for letting me ramble!