Just a note about Mr. Waters. David Gilmore actually played a lot of Waters' bass lines in recordings. Not to take anything away from Roger, but he was definitely my least favorite member of Pink Floyd. My favorite? Mr. Richard Wright, RIP! Tony Levin is a FANTASTIC bassist! Man I love me some Liquid Tension Experiment. And, he also has worked with two of my favorite drummers (Steve Gadd and Bill Bruford) among other fine drummers like Mike Portnoy (for you Dream Theater fans.) I'm just thinking of a very underrated bassist, Trevor Bolder from David Bowie. he had some pretty grooving bass lines. But if we start moving to the "groove" style of bassists... what about Aston Barrett from the Wailers (Bob Marley's backing band)? He was very influential as well..