@

The at symbol (or @) on your keyboard is made by pressing the Shift key and the number 2 at the same time.

Real Life Usage

These are examples of where the at sign is used in real life.
*[[WPD]], The usernames all have an @ in front of them.
*[[Twitter]], the usernames are always followed by @.
*[[IRC]], in some IRC networks, your nick name is followed by @.
*Email addresses, the @ symbol is commonly used in email address formatting.
*[[Emoticons]], sometimes the @ symbol is used in emoticons, such as @_@. [[Hackers]] think they're cool for using these.
*Insults, sometimes used when calling somebody a [[Grand Theft Auto|tw@]] (twat), which is a slang for a [[vagina]].
*Replying, this is frequently used when replying to someone, either on a forum, or some other [[4chan|messageboard site]] that doesn't have a quoting system. For example, somebody might say @shitposter... and then write their message.
*Laziness, some people might use this because they're simply too [[lazy]] to type the full two-letter word.