rm -rf --no-preserve-root /

LPT: scarred of running accidentaly rm -rf --no-preserve-root / or rm -rf ~/ ?

Do sudo touch /-i, touch ~/-i and touch ./-i in the most important directories you have. When you will type rm -rf / accidentally, the -i operator will be added in the command and rm will ask you for confirmation to delete EVERY SINGLE FILE of the directory you're removing. Then, just abort with Ctrl-C

Explanation : touch is used to change the "ladt modified" date of a file, without changing it's content. If the file doesn't exist, it creates it.