So many of a time you see an article about ssh autocomplete that reads your known_hosts file. Well that great and all but what about just reading your ssh config file for all your pre-configured hosts. Well here is the code to do it. Just add it to your ~/.bash_profile or ~/.bashrc file.
if [ -r ~/.ssh/config ]; then
complete -W "$(echo `if [ -r ~/.ssh/config ]; then cat ~/.ssh/config; fi | grep Host | cut -f 2 -d ' ' | uniq`;)" ssh