Grinning, ducking, and running. Implies that my post will result in something being thrown at me.
The angle brackets imply that what is inside is an action, such as <waves>. Used mainly on Internet newsgroups, back before all the social networks.
Occasionally additions are made, such as <gd&rvvf> which means grinning, ducking, and running very very fast. Sometimes ffa (far far away), etc. You get the idea.
SHE: I bought new boots today. <happy dance>
HE: Are you up to 100 yet? <gd&r>
SHE: <throws boot>