I frequent so few forums that I have a pretty shrewd idea of where online I must have met the person concerned.
If it is just a one off he/she did out of 'red mist' then is nothing you can really do.
If they hit your site again though and they are using the same proxy or a proxy within an easily identified range and they aren't too bright then you can 'play' with them just for a giggle using .htaccess.
My favorite on some sites is just redirecting the ip to another page set to fullscreen with menubar, toolbar, scrollbars and resizable values set to 0 - then putting whatever I feel is rather annoying at the time. Things like loud sounds going 'boo' which then redirects quickly to an identical page and back again.
This can backfire as it has a tendency to somewhat annoy morons like that.
Edited by deleted (Tue 27-Oct-09 13:55:41)