There is a person in my Gmail chat friend list which I don't like. When I'm online, he gets notified (while my status shows I'm online).
I'm talking about my Gmail Web page and default Chat box in the left side column.
You can’t show online/offline selectively for different contacts. However, you can block different people which you don’t want to see when you are online.
That’s it; you don’t need to remove the respective person from the Contacts.