Uh... I just got my first rage message.
I feel almost kind of proud, since I am not really all that good (as my stats will show). 
 
"learn moves cunt" 
 
Granted... From his point of view I might as well ONLY have known smoke-bomb, teleport-punch and air-throw (played Smoke obviously)
- but honestly... 
If you're unable to do ANYTHING at all against it... What makes one instinctually accuse your opponent of being bad at the game.

Anyway...  

Sign if you've received rage messages :-)

"learn moves cunt"

Once long ago. Guy kept jumping in the air to attack me using Ken, but my Guile kept catching him mid-jump and follow it up with a back-breaker.
 
"Piece of shit cheesed Guile" he said.

Nothing tops the 5 voice messages an angry dude sent to his defeater after a GG message 
 
"You're so nice, you're so nice, you're so ice and nice, you're ice" 
 
Brilliance !

You should see all the rage messages I get while playing Gears of War 2. Apparently killing somebody instantly means that you're host and therefore are the worst person to ever grace the Gears of War 2 servers.

I love it when I beat someone who is a higher rank than me in SSF4 and then get rage messages with all the excuses of why they are still better than me and how I suck.

@EvilDingo said:

"learn moves cunt"

It's so simple; almost elegant.

The best one i have got is after i kept blocking a smokes teleports he then quit out and said

*you're playing the wrong game turtle you fucking suck.*