Sometimes you simply need to dump out the contents of a text field raw, and not have the SharePoint field controls alter you HTML, strip scripts, etc. 

I’m currently using this to display raw HTML that is being programmatically imported into a list.

This is a very simple example of how to make a field control, however you’ll want to ensure you consider things like caching and security before deploying this.

    public class RawTextFieldControl : BaseFieldControl
    {
        public XnaRawTextFieldControl()
        {
            base.DisableInputFieldLabel = true;
            base.ControlMode = SPControlMode.Display;
        }

        protected override void RenderFieldForDisplay(HtmlTextWriter output)
        {
            output.Write(this.ItemFieldValue);
        }
    }