No long lines. Limit the line length to a maximum of 120 characters.

In my book, 120 characters is a very long line. When editing code I didn't write, I always leave the formatting as is. It usually isn't my writing style, but I can write Perl even if it doesn't have the spaces where I usually put them. I'm not at all a fan of enforcing formatting - I find that as counter productive as enforcing wearing ties or high heels.

But there's one formatting thing I change when editing code. And that's breaking lines exceeding 80 characters. I've my own set of stylistic issues (which I don't enforce, or want to enforce on anyway - they are just for myself), and each point will be broken once every blue moon for some reason. Except the 80 character line limit. That never, ever gets broken. 80 characters is the absolute limit a line may have.