Atlanta at 2011-01-28 12:22:54:

How about the controversial (studio requested, positive note for audience) Blade Runner epilogue:

Deckard: [narrating] Gaff had been there, and let her live. Four years, he figured. He was wrong. Tyrell had told me Rachael was special. No termination date. I didn't know how long we had together... Who does?

youtube, quote starts 50 seconds in.

Amos at 2011-01-28 12:40:03:

Goodfellas and Animal House leap to mind. One is fairly necessary and adds something. One is hilarious and adds something.

Scott at 2011-01-28 13:05:31:

@Amos: Let's see Bluto becomes Senator Blutarsky, Niedermeyer gets shot and killed in Vietnam... by his own men, Otter becomes a Beverly Hills gynecologist. Feel free to chime in on the others.

midwinter-az at 2011-01-28 15:40:15:

The first one that comes to mind is Mallrats where they run down what happened to everyone after that infamous day at the mall. Not exactly high cinema, but a college favorite of mine :)

Adaddinsane at 2011-01-29 04:07:20:

You ask about the guidelines for a spec script? I suppose you just need to answer this question:

Has the story finished?

Scott at 2011-01-29 08:52:21:

@Adaddinsane: And that has just become my official answer to the question as to whether a writer should include an epilogue or not. Thanks for that succinct point!