I’ve always been partial to Tony the Tiger.
Hands down, no brainer, Flat Eric.
Actor Geoffrey Holder.
The one in the middle.
http://www.americanphoto.co.jp/photosearch/Previews/PLX071931.jpg
Anna-Marie Alberghetti! The good seasons lady!!
Does anybody but me even remember her?
Or, alternately,
Hey Kool-Aid Man!
OH YEAAAAAAAAAHHHHHHH!!!
This was going to be my answer. And this wins hands down. An advertising campaign that, in the end, became so iconographic with the american frontier that he’s passed into folklore along such (real life) legends as ‘Johnny Appleseed’, ‘Davy Crockett’, and ‘Daniel Boone’.
All the others mentioned are fine characters, it’s true. But Bunyan has made it into Legend.
When I was a kid I was crazy about Farfel the dog, who did singing commercials for Nestle’s chocolate in the 1950s. I had my own stuffed toy Farfel, and I ran around the house driving the adults crazy singing the Nestle’s song in a Farfelesque voice. I was also very fond of the Speedy Alka-Seltzer commercials. But since I liked chocolate better than antacids, Farfel won out.
Dosen’t anybody remember avoiding the Noid?
And the Frito Bandito? (Now, I imagine, very un-PC)
I miss the Hamburgler, myself. Rubble, rubble.
“First time in a limo… this small.”
I loved that ad.
Long ago, some adman gave us the little cartoon lady in the water softener commercial.
Pitchman: “…so call your Culligan man.”
Lady: (hollering) "Hey, Culligan Man!"
The startled Pitchman was usually bowled over by our leather-lunged lady’s “call.”
Her debut was in black-and-white TV, and she’s still around.
The fight against ignorance. Our slogan is “Fighting Ignorance Since 1973 (It’s taking longer than we thought).”
Oh. So I stand corrected. Very informative link, and now I know. I don’t see why Hal had to be a condescending dick about it, though.
Either Marshie, or those poor Naugas.
N-E-S-T-L-E-S, Nestles makes the very best …CHAAAAAWWWWWWWWW-clate.
The Gadget Freak who drags his wife outside to show her how he can roll down all the windows in his Jetta with one turn of the key in the driver’s door.
Tony the Tiger.
The Exxon Tiger.
The Uniroyal Tiger Paw Tiger.
Juan Valdez.
Mrs. Olsen.
Robert Young’s decaffeinated version of Mrs. Olsen.
Granny Clampett selling Winston as tasting like a cigarette “had oughta”.
The cartoon engine taking a shower in Mobil Detergent Gasoline.
The Taco Bell Chihuahua.
The guy in the Hawaiian Shirt offering his clueless buddy many variations of a “nice Hawaiian Punch”.
*Note: The pictures are work-safe, but the comments that follow aren’t.
Somebody else remembers Farfel!!! You’ve made my day, twickster. 
(Scroll down on the second link, last two pictures are from the Eneman CALENDAR!! The mind boggles.)
Was he the dude in the sequined suit, said “Crisp and clean; no caffine. Never had it. Never will,”? He was cool.
I always liked McGruff the Crime Dog.
I can’t believe nobody’s mentioned:
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Raymond of Phillips Milk of Magnesia. When will he lose that loudmouth of a wife? Sheesh! And I could have sworn I saw 'em in a sudafed commercial recently.
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The Country Crock Disembodied Hands. They were around long enough to have a kid, fer chrissakes.