The Hopwire Grenade, sometimes simply known as Hopwire, is a weapon cut from Half-Life 2. It can be found in the playable Half-Life 2 leak. Although it has the same entity name, it is unrelated to the Vortex Hopwire cut from Half-Life 2: Episode One.
Such a weapon, once placed, leaps up into the air after several seconds and shoots out several wires which, when tripped, cause the grenade and all its tethers to detonate.
It was to be used by the Alien Assassin. It is likely but unsure if the player was to acquire their first Hopwire Grenades after killing an Alien Assassin.
As seen in the Half-Life 2 leak source code, the Hopwire Grenade was originally to be the weapon of choice against Striders, replaced in Episode Two by the Magnusson Device. This is confirmed in the Episode Two commentary, in which Valve's Joshua Weier states that the Magnusson Device "started life as a Half-Life 2 weapon called the Hopwire".
In the playable leak, the Hopwire is extremely unstable and does not work properly. If one of the wires touches a surface in the wrong way, the game will crash.
When held by the player, it uses the regular MK3A2 Grenade model. The proper model will only appear when it is thrown and can be separately viewed in the game files.