Sony is a major computer and electronics manufacturer and, in the world of Megatokyo, Ed's employer. In the early comics we see Sony making a bid on the hostile take over of Hell, but will not accept Satan's high price on such an 'out-dated operation'.
See the Wikipedia entry on Sony for further information about the real company.
Sony are also the manufacturers of Ping. As a result, Dom has been sent by rival company Sega to get hold of her. Much to Largo's surprise, Ping is 'pretty soft for a Sony' after she offered Piro her lap to sleep on. Though it was not until after she passes into Piro's possession do the Sony Labs finally run a simulation of her rejection protocols. As a result, Largo's pleasant surprise evaporates into fear and wariness.
A huge piece of kit Ed is kitted out with from around the time he takes over Largo's English class. Carried in a large briefcase and a massive drain on the power grid, the Killtrunk is used by Ed in an attempt to eliminate Ping. But it is presumably destroyed when the Space laser destroys the school.
Kill Balls are a special offensive unit. Initially Ed uses one during the city battle with the Zombie army. Upon encountering Miho, he acquires greater numbers in an attempt to defeat her.