What popular hacks are known for slowing down small forums?
 

I know the Shoutbox can, but what else?

Thanks.

Any mod you make is going to make it slower...you can't really say any in particular. If you want a fast forum get rid of them all. :p

Just look through the mods, ones which run a lot of code and queries multiple times (like in the *bits) will be likely to decrease your performance levels, thats about the best advice really.

The thing is, I'm making a topic in my forum to say that we won't be taking any suggestions for certain hacks (server heavy ones), so I'd like a list. :)

I don't think its possible to make any definative list of 'heavy' modifications. Everyone's experience is different, depending on the type of host equipment being used, how many users are on the forum, and interaction between modifications installed (intentional or otherwise).

For example, I do not agree with you saying that the Shoutbox is one of those 'heavy' mods, simply because I have never found it to be a problem. However, on a forum with thousands of members using it, then it could be a problem.