<txp:if_first_article> and <txp:if_last_article> work as the names suggest: when placed inside an article form, they’ll display their contents only on the first or last article in a <txp:article /> or <txp:article_custom /> list.

<txp:if_different> can be used in any kind of list (article, link list, etc). When repeated, it will display its contents only if it’s different to the last time. For example, here’s an a quick archive list organized by month:

Page template:

<txp:article_custom form="month_list" limit="5000" />

month_list form template:

  <!-- heading - only once per month -->
  <h3><txp:posted format="%B %Y" /></h3>
<txp:permlink><txp:title /></txp:permlink><br />