I have seen this feature in other forum scripts and I found it useful: Forum-based topic prefixes.
How it works: You can set different prefixes for each forum in ACP, so that users can choose any of them when opening a new topic. This prefix is shown before the title (e.g. [MOD] Topic title, [TEMPLATE] Topic title,...). If no prefix is chosen by the user, topic title is shown as is.
This usually has to be done by an Administrator/Moderator editing user´s topic title.
I think this feature helps search feature to be more efficient (searching prefixes), with the advantage to have specificly clasified topics for each forum.