The title says it all.
I can think of three.
Napoleon Dynamite:
Kip and LaFawnduh’s wedding.
Harry Potter and the Chamber of Secrets
Gilderoy Lockhard appears on the cover of the The Daily Prophet, wondering who he is.
Ferris Bueller’s Day Off
Ferris tells the audience to go home.
What else?
The Hitchhiker’s Guide to the Galaxy.
Les Triplettes de Belleville Not really important but why not a spoiler?Guy who rented the paddle boat to the old lady is standing at the shore looking out to sea. Then he looks at his watch.
Oops, sorry:
Animated sequence showing a battlefleet heading to Earth where, because of a horrible miscalculation of scale, it is eaten by a small dog.
28 Days Later.
Priscilla Queen of the Desert
Blues Brothers 2000
A Knights Tale
SHREK 2 has a very important one. Dragon reunites with Donkey and brings their kids.
Do you count movies with scenes intercut with the closing credits? If so, Dodgeball and Dawn of the Dead qualify.
Oh, and if you count movies that include bloopers in with the credits, there’s Cannonball Run and Dude, Where’s My Car? too.
You can browse this [url=http://us.imdb.com/Search/crazy-credits]section* of IMDB.
Wayne’s World, if we’re going by Otto’s standard.
Jay and Silent Bob Strike Back:
God (Alanis Morissette) closes the book on the View Askewniverse, literally.
Pirates of the Caribbean: Curse of the Black Pearl
Amazon Women On The Moon
Grumpy Old Men II, which has bloopers, including one of the funniest things I have ever seen, by Burgess Meredith.
In Airplane! the post-credits scene is of the guy in the taxicab that Ted Striker abondoned saying something like “That’s it, I’m only waiting another 15 minutes”
(or words to that effect. 
)
I was in Hawaii once… Ohiwannalayya.
Dawn of the Dead (2004)
Ving Rhames & co escape on the boat, run out of food, and wind up trapped on a zombie infested island.
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Daredevil, the non-director’s cut
Married to the Mob – Michelle Pfeiffer and Matthew Modine having fun…
Miracle – a very short clip of Herb Brooks addressing the actors/hockey players.
Flirting With Disaster has comic bits intercut with the credits.
Being There – but I don’t remember if the Peter Sellars outtakes were intercut or added to the very end.