"Fixing E.T. for the Atari 2600"

This guy: http://www.neocomputer.org/projects/et/
ROM hacked the original ET game for the 2600, to fix most of the bugs, flaws, and idiosyncracies. His write up of the entire process is quite in depth, and I found it an interesting read.

It was interesting. I'd never played ET before. But I've always liked that idea of trying to fix a broken game.