[jwr]

I would add to this list:

If you are intercepting UNIX signals (starting with SIGINT), go back to the drawing board and think again. Don't do it. There is almost never a good reason for doing it, and you will likely get it wrong and frustrate users.

[pjc50]

I wrote one of these ages ago that was very useful (regain interactive control of an otherwise batch program) but broke all sorts of 'rules', including doing blocking IO in the signal handler.

[edwintorok]

How about cleaning up tempfiles on ^C?

[renox]

YMMV but I prefer cleaning the old tempfiles at start-up. It allows you to get the content of the tempfiles after the program stopped, very handy for debugging..