weapon_hopwire
Entity description

A recently discovered "black hole" grenade whose explosion will create a black hole vortex strong enough to even destroy striders. Is first thrown and then activated by a second attack press, like a remote mine.
While not in any currently released Valve product, this weapon can be enabled (so far seen in ep1 and smod) by entering the following into the console:
hopwire_vortex 1
give weapon_hopwire
or give npc_grenade_hopwire
This will provide you with only one hopwire. An additional 5 hopwires can possibly be obtained through typing impulse 101
into the console Not sure if impulse 101 works with it, Doesn't in portal..
You can also have them in Source SDK-Hammer by going into a entity, Then changing the name to weapon_hopwire and hitting enter then apply. It will come up as "Obsolete" with the special image but it DOES turn up in-game.

Legacy
The name "Hopwire" was taken from a grenade originally intended to be in Half-Life 2, which would, when thrown 'hop' into the air, and shoot out tripwires to nearby surfaces. If the tripwires were broken, the grenade would detonate. The old Hopwire can be used in the mod "Missing Information".
Keyvalues
[Todo]
Flags
[Todo]
Outputs
[Todo]
Inputs
[Todo]
Resources
http://www.halflife2.net/forums/showthread.php?t=110926 - Forum thread about the grenade.
http://www.joystiq.com/2006/08/06/the-hl2-episode-1-black-hole-grenade/ - Article with movie.