What is this Glowing ball?

[Admin_Winnuting]

Hey all,
In this HL2 movie I have it shows a glowing ball thing that Gordon shoots and doesn't look like he destroys it.

I got some images of it below, Can anyone tell me what it is?
PS: Sorry about the poor quality, This movie wasn't in Bink format.

Glowing ball
Ball being shot
Ball not glowing

By the way it does seem to want to hurt you.

 

[silverstealth89]

i forgot the name but that ball rolls around and attachs itself to your car and every so often it will give substantial amounts of electric shocks. so get out of the jeep take the anti gravity gun and pick them off like barnacles. then blast them off the edge of a cliff

 

[burner69]

It's a roller mine. Yeah I'm pretty sure they're intent on hurting you. Looks like a bit of machinery the combine made - like scanners. At the start of that vid you see them interferring with your buggy's steering (not like THAT).

 

[Alieni²]

Spoiler

Its a roller mine...
------------
Roller Mines
Attack: Rolling into you/your vehicle
Threat: Low
Another feat of Combine engineering, roller mines will prove to be a thorn in Gordon's side. These deadly spheres will roll at you doing damage or latch onto your vehicle, throwing you off balance. While not readily destroyed, the manipulator or shotgun can send the mines flying out of range.

^^

 

[InvaderScooge]

http://www.halflife2.net/index.php?page=enemies

Rollermines

You'll find these rollermines scattered across the many roads outside City 17. If you're driving a vehicle these little things will try to attach themselves and disable it. If you're on foot they will zap you with electricity. They're not easily destroyed but a push using the manipulator will throw them out of range.