This is my quick off-the-top-of-head list. OK, great choices, but Gary Larson should be there. He's one of the few cartoonists I know who "regular people" (people who are not crazy about cartooning) know by name. Heck, EVERYONE has a book of FAR SIDE cartoons. And a lot of cartoonists, pro and am, have been influenced by him.
Chris Sims writes about Gary Larson's sense of humor and shares some funny stories at ComicsAlliance.