There might be the case when you don’t wish to chat with few peoples or in other words you want to chat with the selected one. If you get frustrated with the disturbance caused by these “No to Chat” people, in that case, Facebook provides you with the nice facility which enables you to choose the people with whom you don’t want to chat.
It’s a hidden feature which can be enabled by following these steps:
Step 1: Open your account on Facebook.
Step 2: Click on the “Chat” option which is present on the lower right side of your profile.
Step 3: There you will find two options. Choose “Friend List”.
Step 4: There you will find an option of creating a new list. Name it, for example, “Blacklisted”.
Step 5: Now, select or write the names of the people with whom you don’t want to chat.
Step 6: Set the status as offline for this chosen list.
Hide From Some Facebook Friends
Reference : http://pctipstrickshacks.com