on the internetz the exclamation mark is needed when stated by it's self; when used in a sentence the exclamation mark is optional
when the word is used irl it should not be said by it's self.
unless your friends are hip and know you're not saying "when!"
"fuckin win dude!"
gr3g- ii got 2 toiyz in mi kidz meal nigga!
This can be made stronger by adding epic before it, as in 'Epic win!'.
"This thread is made of win"
"WIN! DO WANT!"
Person 2 "WIN"