Thus says the Lord (Yahweh), “Do not learn the way of the nations, And do not be terrified by the signs of the heavens Although the nations are terrified by them;Jer 10:2 (NASB)
Halloween is a pagan festival and should not be observed by Christians. Many of the things you read on this site are arguments against pagan practices that have been syncretized into Christianity. Halloween is unique in that it has never pretended to be something that it is not. It is an evil day, created by an evil force, and practiced in an evil way. There is no redeeming value in this holiday whatsoever for a Christian. In fact, many mainstream Christian churches are stopping the practice and holding alternate functions to give families something else to do on this night. Satan must be laughing hysterically at the Christians who keep his holiday.