These history substitutions could be covered.

Should mention global search/replace first, as that is more commonly what is needed.

The ^x^y is a quick trick but users need to know it only does first substitution, which can make it highly error prone. More info:
http://stackoverflow.com/questions/2280778/unix-commandline-history-substitution-foobar-for-multiple-replacements

Common error — doesn't do what you'd hope:

mv foo.txt foo.bak
^foo^bar

Now you just ran mv bar.txt foo.bak and clobbered your foo.bak backup file!