It's kind of a dead giveaway, but it's probably not too bad.
A file extension of is a dead giveaway, as is the copious use of tags that begin with g:.
Try closing your eyes. This is a dead giveaway as you cannot close your eyes in astral form.
The obtrusive presence of edge case possibilities is a dead giveaway for user interfaces designed by programmers. Dialogs, controls, and options that are used a hundred times a day sit side by side with dialogs, controls, and options that are used once a year or never.
A return address with words like "United States Penitentiary" or "correctional center" is a dead giveaway.
Mother tried to hide her feelings,but the tears in her eyes were a dead giveaway.