Stalker

From Half-Life - Wiki on Neoseeker

Stalker
Affiliation	Combine
Hometown	Unknown
Date of Birth	Unknown
Equipment	Laser
Rank	Slave

"On my God, its a Stalker cart." - Alyx Vance

The Stalker is a normal human being, tortured and mutilated by the Combine. A majority of their brain function has been removed, their limbs have been replaced with metal parts, and most of their body has been distorted. The sole purpose for these creatures is to do the grunt work for their Combine masters.

Here is a scene from Half-Life 2: Episode One, where Gordon and Alyx escape from the Citadel, in a cart full of Stalkers.