You are using the my pointer in the gun_shoot action. That is not allowed as gun_shoot is not attached to an entity. I guess what you wanted to do was:

Code:
action gun_shoot()
{
	ent_create("muzzleflash.mdl", vector(my.x + 130, my.y, my.z + 9), gun_flash);
	you = ent_create("bullet.mdl", vector(my.x + 135, my.y, my.z + 9), ball_fall);
	your.tilt += 15;
	wait (10);
	your.tilt -= 15;
	set(your,PASSABLE);
}


Always learn from history, to be sure you make the same mistakes again...