Htflags

A per-actor property, this controls special flags for sprites.

Internal Name	Provided CON Label	Value	Description
SFLAG_SHADOW	SFLAG_SHADOW	1	Generates a shadow. See spriteshadow.
SFLAG_NVG	SFLAG_NVG	2	Turns palette 6 whenever night vision goggles are used. See spritenvg.
SFLAG_NOSHADE	SFLAG_NOSHADE	4	The sprite's shade is unaffected by the shade of its sector. See spritenoshade.
SFLAG_PROJECTILE		8	Is a projectile.
SFLAG_DECAL		16	Prevents teleporting. The sprite is not entered into the decal deletion queue.
SFLAG_BADGUY	SFLAG_BADGUY	32	Is an enemy. See useractor.
SFLAG_NOPAL	SFLAG_NOPAL	64	Sprite will be insusceptible to floor palette of sector containing this sprite. See spritenopal.
SFLAG_NOEVENTCODE	SFLAG_NOEVENTS	128	Sprite will not be run through EVENT_GAME or EVENT_PREGAME.
SFLAG_NOLIGHT	SFLAG_NOLIGHT	256	Sprite will not emit hardcoded Polymer-based lights.
SFLAG_USEACTIVATOR	SFLAG_USEACTIVATOR	512
SFLAG_NULL		1024	null sprite in multiplayer [internal, do not use]
SFLAG_NOCLIP	SFLAG_NOCLIP	2048	Sprite will call "clipmove()" with a clipmask of 0, skipping collision detection with other sprites to increase performance. (Specifically, to prevent runtime behavior that is quadratic with the number of sprites.) Useful for particle effects.
SFLAG_NOFLOORSHADOW		4096
SFLAG_SMOOTHMOVE	SFLAG_SMOOTHMOVE	8192
SFLAG_NOTELEPORT	SFLAG_NOTELEPORT	16384
SFLAG_BADGUYSTAYPUT		32768
SFLAG_CACHE		65536
SFLAG_ROTFIXED		131072	rotation-fixed with respect to a pivot point to prevent position diverging due to roundoff error accumulation
SFLAG_HARDCODED_BADGUY		262144
SFLAG_DIDNOSE7WATER		524288	used temporarily

htflags is a bitfield, so add together the values you want and then set htflags to the sum.
This member can also be set using the per-sprite form of the spriteflags command.