5punk

Blackhole Bomb

in console first type

"hopwire_vortex 1"

then

"give weapon_hopwire"

now throw it and then press attack again to activate it. It is preferable to do it in an area with lots of physics objects, I also suggest you stand back lest you wish to be crushed into singularity.

http://www.youtube.com/watch?v=jn1TjZzO9Yk

Try "givecurrentammo"* after that too, as you can't use "give weapon_hopwire" twice.
The hopwire votex bomb should appear as a second grenade in your HUD.

Watch out for Alyx- she loves to get sucked in. Oh yes.

*There should be a "give item_ammo_hopwire" command too, but I'm not sure exactly what it's called.

edit:
"givecurrentammo" doesn't appear to work for many weapons. However, "sv_cheats 1" followed by "sk_max_hopwire 8" and "Impulse 101" will give you eight Hopwire Vortex bombs. (Eight seems to be the maximum)