Problem
The authenticity of host 'example.com (1.2.3.4)' can't be established.
RSA key fingerprint is ab:cd:ef:12:34:56:78:90:ab:cd:ef:12:34:56:78:90
Are you sure you want to continue connecting (yes/no)?
Solution
ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no
Make sure you understand the security implications of doing this (Hint: they're not good).
(source)
A piggy bank of commands, fixes, succinct reviews, some mini articles and technical opinions from a (mostly) Perl developer.