How can I ensure certain items always display at the end of a list?
How would you like to identify that particular entry? If you're happy to hardcode its id, then I'd do it like this with the filter filter and the without filter:
{% set allEntries = craft.entries.section('products').all() %}
{% set pcEntry = allEntries|filter(item =&gt; item.id = 1234) %}
{% set entriesWithoutPC = allEntries|without(pcEntry) %}

You can now output those however/wherever you like, e.g.
&lt;ul&gt;
  {% for product in entriesWithoutPC %}
    &lt;li&gt;{{ product.title }}&lt;/li&gt;
  {% endfor %}
  &lt;li&gt;{{ pcEntry[0].title }}&lt;/li&gt;
&lt;/ul&gt;