National Lampoon's Vacation would be 10x better if the owner of Wally World at the end decided to press charges. Instead of snapshots of everyone riding rollercoasters, it had mugshots and Clark planning their next trip to Wally World
I've read rumors on the internet that there was at least talk of it ending with Edward Norton shaving his head after Danny gets shot.
If you read the comic Batman when the "Jason" Robin was murdered by the Joker (a four-part graphic novel series that came out around 1990), Batman tried to kill the Joker. The Joker was shot (by his own goon), and Batman left him to die in a helicopter explosion (he survived, of course) on purpose. Batman has broke his rules before in the comic. The should have killed the Joker off. Use CGI to have him land on a police cruiser or some shit. Rumour has it they're using The Riddler for the next movie, anyway. Oh, and whoever said Harvey Dent survived at the end of Dark Knight earlier, try watching the movie again. Pay attention to the part at the end when he dies. And Batman killed him. Tah-dah. He broke huis rules. No going back.
Something About Mary: I always thought it would have been sweet to have Michael Vick have the QB cameo at the end instead of Brett Favre, then he could have used one of his pit-bulls to just massacre that little dog and shown Mary his pimp hand. I'm not a huge fan of Cameron Diaz but she was slammin in that movie, the part I would honestly change is seeing her breasts instead of wrinkled Magda's.
Focus: I didn't like the ending of Death Proof. I thought it would have been a lot better if Stuntman Mike ended up crashing his death proof car, getting trapped in it and burning alive. That would have been a nice ironic twist instead of him getting his ass kicked by some girls.