Anecdotally, I think that much of the short-term aggression associated with videogames is a measure not of the inherent evils of aggressive play but of breaking players out of a context where aggression is permissible — a game world — and then asking them to quickly shift into a real-world context where that aggression is unacceptable. And then there's the burst of aggression we all tend to feel when someone interrupts us while we're deep in concentration, whether playing a videogame, reading a book or trying to catch a game on TV.
As far as anecdotes on the subject go, this one is a tragic doozy. A Texas teenager has been accused of beating a 23-month-old girl to death with a game controller after she interrupted his gameplay. Although he initially denied the charges, 17-year-old Ethan Wolfe eventually confessed to striking the infant with a gamepad. According to police in Tomball, Texas: Police say Wolfe didn't initially realize the baby was unresponsive. It wasn't until he went to check on her that he knew something was wrong. Wolfe is being charged with injury to a child in the first degree, which carries the same punishment as murder. [via KIAH TV][Wolfe] said he was playing a video game, that the child had got in the way of the game, and possibly (relieved herself) on him. It frustrated him and caused him to loose the game. He struck the child three or four times with the controller of the video game. Then he picked the child up, and threw the child up on the bed.