Usually used in MMORPG's, such as World of Warcraft
"LEEEEEEEEEEEROOOOOOOOOOOOOOOOOOOOY!!!" <---this is when the one-man charge, or "leroy moment" happens
"OK, he just ran in there... come on, help him!"
changes his mind about who he likes every few days and has the ability to ignore someone indefinitely.
BUT he can also be pretty sick and awesome friend and is fun to be with.