@StuartH weird, it should look like this: http://i.imgur.com/41sOsUs.png
Anybody thought about a WebRTC integration. To start calling and chatting with other users.
To give you an impression look at https://twelephone.com/
We have a game topic where users have to find from which movie the image is coming from.
We are keeping points at each winning, but maybe a plugin could do that, with a topic header reminder, and a list of users to attribute the point.
Just an idear 
Just another idea I came up with for a plugin...
In the topic view, if post count is greater than a preset number.. hides all trivial posts ex. "thanks!", and/or displays posts with high amounts of favourites only
Maybe a more simple version to start with just collapses trivial posts. This could be done entirely client-side, so a easy plugin to make I think!
+1.
Another one we were discussing on Skype earlier: a plugin that accesses filter:posts.create (see: skype emoji, @mentions plugins) and checks for links to other topics (regex for domain.com/topic/?). If match, creates a post in that topic under that user mentioning that the user posted about this topic, exactly like how Github issues work
psychobunny referenced this topic in link
or similar
(edit: I just thought of the potential infinite loop there, gg :P)
Skype-style popups when people come online. If you are following a user, throw an app.alertand say the user came online, clicking on it takes you to their userpage.
EDIT: somebody above said this thread should be pinned, if you guys keep coming up with brilliant ideas this topic will be first on the list regardless, so keep it coming! 
Would love a CDN plugin. This would be great for forums that aren't just accessed in one location.
Edit: I'm always the one with the uncreative and practical ideas. (Not that the other plugin ideas are impractical, it's that they're creative.)
Maybe somesort of portal system like phpbb and smf has? http://custom.simplemachines.org/mods/?mod=1104
