I have a set of FAQ entries. Each entry has one or more categories attached. To be able to filter entries related to a category I need a list with unique categories.
Using my solution I'm getting all (some double) categories.
{% set entries = craft.entries.section('faqs') %}
{% for entry in entries %}
{% for category in entry.faqCategory %}
<li><a href="#{{ category.title }}" class="filter" data-filter=".{{ category.title }}">{{ category.title }}<ins> </ins></a></li>
{% endfor %}
{% endfor %}