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	Has been defined with defineprojectile.
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	Actor will stay inside its original sector.
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
SFLAG_NODAMAGEPUSH	SFLAG_NODAMAGEPUSH	1048576	Actor should not be pushed back when damaged (by default TANK, RECON, ROTATEGUN, and the bosses)
SFLAG_NOWATERDIP	SFLAG_NOWATERDIP	2097152	Actor will not appear to sink into the floor in sectors tagged Above Water (lotag 1)
SFLAG_HURTSPAWNBLOOD		4194304	Actor will spawn blood as hardcoded enemies do when hurt
SFLAG_GREENSLIMEFOOD		8388608	Actor can be eaten by GREENSLIME actor (Protozoid Slimer). Can only be set outside of actor and event code whereupon it is applied to all sprites of the same picnum e.g. "spriteflags NEWBEASTHANG 8388608" will make all NEWBEASTHANG in the entire game into greenslime fodder.
SFLAG_REALCLIPDIST	SFLAG_REALCLIPDIST	16777216	Actor will always use its set clipdist instead of one potentially overridden in hardcoded circumstances based on its xrepeat and picnum

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.