Lots of people know about the hidden arrow between the E and the x in the FedEx logo. Did you also know:

• The face in the Goodwill logo is the same as the G.
• The old Northwest Airlines logo used a northwest-pointing compass to turn the N into a subliminal W
• The logo for the Big Ten conference has a negative-space "11", since there are eleven member schools.
• The smile-ish swoosh in Amazon.com's logo is also an arrow pointing from A to Z
• The mitt in the old Brewers logo is made of the letters M and B, and the Minnesota Twins logo has "win" underlined

Mostly taken from reddit.