Identifier: forumlist_body_category_before
Identifier: forumlist_body_category_after
Identifier: forumlist_body_subforums_before
Identifier: forumlist_body_subforums_after

Prosilver Location (if applicable): forumlist_body.html,various places.
Subsilver Location (if applicable): same.

Explanation: these events allow extensions to add various contents to the forumlist or modify it.
Use case: Advertisements (as usual). Adding any content above category header of after it (for example - category description, like Show Category Description in Forum Index MOD. Adding contents before/after subforums list or modify its layout ( for example, like List subforums in columns MOD).