Connecting without Host Key Error

To do a one-time connect without errors:

ssh -o StrictHostKeyChecking no -o UserKnownHostsFile=/dev/null <hostname>

(I have a machine usually running Kubuntu that I sometimes boot into Windows, so encounter host key check failures when ssh'ing to Windows.) (Answer from a comment on this askubuntu)

or put in .ssh/config

Host b
  HostName binky
  StrictHostKeyChecking no
  UserKnownHostsFile=/dev/null

Note, only do this on a LAN where security isn't an issue.