Coca Cola has really fallen off of their game in the last 20 or so years. Before that, they had several memorable campaigns:

Coke adds life
Coke is it
"I'd like to teach the world to sing"
"The pause that refreshes"

I think they are still the #1 recognized word in the world. I'd imagine McDonald's and Nike are up there as well.

Bears, beets, Battlestar Galactica.