Cloverfield

[Alex]

In searching for something else I've found online that the generally accepted version of the post-credits sound is:

Spoiler:

it is reversed audio and when you reverse it back it clearly says "it's still alive." Whether that was Rob talking or audio from a nearby walkie talkie (and thus staticky) seems debated. You can hear the audio reversed here. The sequel implications are even stronger and I dislike it for the same reasons stated above.