The Halo games have!
If you're really curious, I can go into as much or as little detail as you want. There are a lot of reasons behind it, especially if you really get into the why on any of the following, but the simplest summary would be these three points:
1) There's an enormous community of players here. Somewhere over 1000 active if including lurkers, and I am neither kidding nor speaking metaphorically.
2) There are a variety of certain kinds of posts that will appear on every page, appropriately.
3) There are a variety of recurring weekly and cyclical events that cause regular activity spikes (one of which is on Friday mornings, as it is at this very moment, for one example)