Taro's NAVI
From Serial Experiments Lain wiki
Taro uses a small handheld NAVI in the shape of a pistol. It's called a child's gun-type NAVI in Visual Experiments Lain. Its display pops up out of the barrel when the trigger is pulled.
Shou Masatsugu destroys a similar NAVI in Layer 04 by dashing it against a building's rooftop.