Cloverfield
After Beth and Rob are killed under the bridge in Central Park, along with what we can only hope is the creature that's stalking the city, there's one puzzle piece that's left unturned. The video footage they were documenting resurfaces with some jumbled audio that sounds like it's saying "It's still alive."
Man of Steel
When Zod uses his heat vision to destroy skyscrapers around Superman, you can see one pretty prominent poster in the background. "Keep Calm and Call Batman" is pretty clearly on display on one of the cubicles before it falls apart.