I think they exist in advertising, although in America they're supposed to be illegal.

My husband adds Saturday-Night-Live-style subliminal messages (remember the old Kevin Nealon routine on the SNL newscast?) sometimes to comments he makes to me. "Maybe we should go upstairs (hot sex)?" "Maybe you could think about what's for dinner (chicken and rice)."

I need to do the same in things I say to him (turn that football game down), but I rarely think of it.