The other day I watched Leviathan, which couldn't be called good necessarily, but afterwards I saw the poster on google images and just got hit with the power of the way they used to superglue your attention with the tag:

"How long can you hold your breath?"
How fucking cool.
It barely has anything to do with the movie as there's never any threat of being submerged until the end, but it doesn't matter, it just has power. And the way they used to thread them into the trailers was amazing too, often slapping you with one word at a time between raucous climatic action scenes:
HOW (explosion) LONG (guy gets blown through a window) CAN (Fires grenade into the screen) YOU (slow motion collapse of giant structure) HOLD (someone screaming as giant structure descends on them) YOUR (water bursts through windows sweeping everyone off their feet) BREATH? (monster rises to fill the screen howling) - TITLES SLAM ON!
The art of the incredible tag line seems to have been lost entirely. So I'm begging you, please share your favourites here because I absolutely love these, and I'd really like to see the posters too, so link if you got 'em!