Those who advertise, but shouldn't:
The "Got Milk?" campaign has been going strong since 1993, one of the most recognizable advertising slogans in the country. As a direct result, thousands of Americans stopped dunking chocolate chip cookies into soy milk, and hundreds more ceased pouring water over corn flakes.
If people use your product's brand name as the default for all similar products, you're in good shape. (See also: Kleenex brand facial tissue.) The animated polar bear commercials aren't winning the cola war -- you've already won.
The United States Postal Service
I already know you are an option. The mailbox in front of every house in America kind of gave it away.