From Valve Developer Community
1] : Wait Till Seen
- Prevents this NPC from seeing (or being seen) until it enters a player's viewcone.
2] : Gag (No IDLE sounds until angry)
4] : Fall to ground (unchecked means *teleport* to ground)
8] : Drop Healthkit
- Causes this NPC to drop an
16] : Efficient - Don't acquire enemies or avoid obstacles
128] : Wait For Script
- Forces this NPC to "wait" in an idle state until it finishes playing a
256] : Long Visibility/Shoot
- By default, increases a NPC's sight range to
6,000units and allows it to attack from anywhere within that distance.
512] : Fade Corpse
1024] : Think outside PVS
- Allows this NPC to run its regular AI outside of any player's PVS.
2048] : Template NPC
- Marks this NPC as a template for entities like
npc_template_maker. The NPC will not spawn on its own. This is not needed for
4096] : Do Alternate collision for this NPC (player avoidance)
- Note:This flag is disabled in episodic for player companions because the
StartScriptinginput does this.
8192] : Don't drop weapons
16384] : Ignore player push
- Don't give way to player