Everyone knows the Microsoft "where do you want to go today?" Assuming other op systems did that sort of campaign....
Macintosh: Where do you want to be _tomorrow_?
Unix: Do you actually want to get there?
os2: why not go here instead?
Tandy: "Where are we going?"
CP/M: "Oh... we were going somewhere?"
DOS: "Been there. Done that. Wrote the book."
[Submitter's note: these came from the minds of the Hero system Mailing list.]