Laura K. brought our attention to these ads with not-so-subliminal sexual content (via haha.nu). Some of them are so-not-so-subliminal that they may not be safe for work.
NEW (Dec. ’09)! Fresh “shaved” turkey (from The Consumerist):
Ad for a film festival in Barcelona:
NEW (Apr. ’10)! Tom M. sent along a photo of a billboard, advertising Penthouse in Sofia, Bulgaria, with the same visual trick:
Taylor D. sent in these two ads (found here):