Does anyone watch GameTrailers' Pop Fiction videos? They just released a video relevant to dumping.http://www.youtube.com/watch?v=7xkiqneQa4U
The series looks at various rumors/myths/etc. about a wide range of games. This video is about censorship of the NES version of Maniac Mansion. It was already well known that Nintendo demanded a number of changes from the C64 original before they would let Jaleco release the NES port. However, they missed one questionable part of the game, and in the currently dumped USA release of Maniac Mansion, you can actually kill a pet hamster by microwaving it.
The rumor is that there was a second run of carts that took this out. GameTrailers spoke to several people involved with the game, and soon found that Nintendo did make this request, and Jaleco made a modified version. They also found that this version was used for the PAL release. For awhile, it looked like that was all they'd find, but in the end, they found two former Jaleco employees who clearly remembered that they used the hamster-safe version on a second run of carts released in the USA. So, assuming their memories are correct, there's an undumped American version of Maniac Mansion on the NES.