Apple: "1984"

Wow, did this one generate some serious heat when it launched in the early 80's. Now, some might argue that it was a wee bit off-topic for Apple, since it was aimed at IBM (as opposed to Microsoft, which really emerged as its true rival). That being said, the revolutionary spirit of the ad perfectly matched Apple's brand promise, and is a theme that's run through its best ads ever since. (stay tuned for the "Think Different" ads).