My favorite game in highschool (ever?) was Age of Empires II. I still remember that awesome graph at the end (which I spent embarrassingly long amounts of time studying and marvelling at):
I know we already have a cumulative reputation graph on our http://stackexchange.com/ profile (as documented here), but I'd like to see it on all of my profile pages along with daily changes and site-specific badges, etc. For example, I'd like to see the date I earned my c# tag badge. Or perhaps a cluster of Nice Answer badges during that particularly productive week (that I might have some day). I'd also like to see when I earned each privelege (ability to edit posts!).
If we had something like this, I'd probably spend embarrassingly long amounts of time studying and marvelling at it.
(Bonus: easy fraud detection!)
In all seriousness, something more like this, but with the badges, etc., inserted in there somewhere: