First of all this is new to 2.4 and definitely not an exploit but you will be one of the first to know how to do it and continue to keep your rep as one of the kids in the know.
HAVE YOU EVER BEEN IN A GROUP AND SEEN MARKED MOBS? REALLY? ME TOO! AWESOME, WELL WITH 2.4 YOU CAN NOW TYPE THOSE ICONS IN CHAT, WANNA KNOW HOW? HERE IT IS! (everything in caps was edited in for the 5 posts below me with a combined 7 rep so yeah, tired of being flamed. If you knew it awesome, if you didn't I was just trying to contribute and if you need to close this thread because I don't like kids in general that's awesome as well... )
{skull}
{diamond}
{triangle}
etc...
btw, it's {cross} before you ask.
Just type this crap in /chat. /G /1 /2 whatever.... yeah, you will be the sexiest ever girl... I pick 3 what think you?
Have fun and yeah, I've been here for a while so it feels nice to try to contribute something!
Have fun XOXOXO'n yer in game girlfriends......