Folks, you will help servers a lot if you demo these occurrences and report them to the server. Reporting them here means we all look at the demo and think "yup, that's an aimbotter" but are powerless to do anything. Reporting it to the server means that the operator can IP ban them, or even report them to other operators if they should decide to.
The problem with demos here is that people who can do anything about it have only the name to go on, something which can generally be faked easily. Server admins won't see the IP of that name, something which is not so easily faked.
If you can't find out how to contact the server's operator/admins (hey, I can be that dense sometimes...lot of times... :-P ) and you feel you must post here, try to include the server it was seen on, and the date, time, and timezone! This greatly helps admins parse the logfiles for any information that can be gathered from them.