Riot Gear

Overview
Riot Gear is energy-based armor occasionally used by Combine forces to strengthen themselves. It appears in forms of shields, helmets, waistbands, gauntlets, chestplates, etc. Upon being struck by a bullet, melee weapon, or pulse, a moderately large wave-like effect will appear on the barrier, and the armor will lighten. Upon taking sufficient damage, the armor will shatter and vaporize, leaving the body part previously protected as vulnerable. Some projectiles, such as crossbow bolts, are capable of automatically shattering the armor, while other projectiles, such as grenades, will merely bounce off harmlessly.

Notably, some weapons are able to instantly shatter or outright puncture Riot Gear, such as the Karabiner or Magnum.

The frequency of Riot Gear appearing, as well as the gear's durability, depends on the difficulty; from never appearing on Easy, to being somewhat common on Nightmare.

Tactics
-For targets wearing Riot Gear, it's often best to simply shoot a target in an unprotected area. For example, units wearing helmets can be shot in the chest, and units with larger shields (pictured above) can be shot in the feet, even if they are alert.

-If attacking a target's gear is the only option, try using heavier weapons to get rid of it straight away rather than whittling it down with repeated, weaker shots. Powerful weapons like the Karabiner or AK-47 will often do the job fine.

-If you are unable to get any good shots on a protected target, or simply don't wish to waste any ammo on them, you can try lining up the target with another unit, humorously causing one to kill the other with friendly fire. This does not work on higher difficulties, due to enemy friendly fire being disabled.

-If you're forced to melee a geared unit, don't try kicking their armor, it simply has no effect. Go for any exposed areas you can see, or use a high damage melee on their armor or bodies, such as the Sword.