I haven't done a Monday Fun in a while, and realize that this is the last day for a blog contest on this site, so... two great tastes that go great together! Especially since it's something I'd have blogged about anyhow if I ever remembered to. :p
Anyhow, this isn't a game so much as a site for quizzes, so I'm breaking away from the usual format, and doing just a more regular post format. Ooo, you rebel you!
So yes. Sporcle is a site featuring tons of quizzes on a whole plethera of subjects, some made by the site, some posted by users. And the quality I've seen so far is generally good, although you run into a few quizzes here and there that are sub-par.
But you can always go by rating for instance, or most popular quiz, to make sure you get the gems. Or you can just browse a given category that you like. Or go for a random quiz (overall or in a category). Or if you have an account, see what the game challenges you to, and run with it.
If you know other people that play and know their username, you can also follow them, or have them follow you (or both, in which case they're a "friend,") and challenge them to try to beat your score at a given quiz as well.
So, yeah. Fun little time waster to challenge your brain, with a bunch of ways to look around for what you want. Go have fun with it!