go to the console and type in "status". The first column lists the player's number. Type in "clientkick ##", where ## is the player's number.
Just be glad no one with a tilda (~) in their name joined your server...you'd still be sitting at the console (then not sitting at the console), swearing up a storm....
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"If your philosophy does not produce corn, I don't want to hear about it." - Red Bear