There are no new weapons in Episode One but there are 3 new enemies.

Combine Advisor
		Not much is known about the Advisor but it is believed to be the original form of the Combine and hold a high ranking in the Combine order. First Seen: Chapter One, Undue Alarm Chapter Appearances: 1, 2, 4, 5
Stalker
		The ultimate fate of humanity. Tortured, experimented upon and their humanity drained from them, these lifeless abominations can be found within the silently ticking Citadel attempting to stabilize the Core and the remaining systems. Their only attack is that of a laser from their eye panel. It isn’t very damaging, and as such the Stalkers pop up as more of a nuisance than any kind of threat. First Seen: Chapter One, Undue Alarm Chapter Appearances: 1, 2
Combine Zombie (Zombine)
		As a result of the Combines loss of control in City 17, the Combine soldiers have fallen prey to the headcrabs now running amok in the City. With the added armour and agility, the Zombines or more than simply a threat, taking a good four shotgun shots to take down. They also have a knack for suicide runs, priming a grenade and coming charging towards you. If this happens, whip out the Gravity gun and suck the nade out of their grasp. First Seen: Chapter Three, Lowlife Chapter Appearances: 3