You're a Bunch of Factors

The mathematics of poker often shows something to be true that intuitively we did not think is true. This thread will link to all posts where something useful (and not particularly obvious) has been shown to be true. Mods can sticky this thread if they wish. I will update the OP with links.

+ 3-betting With Any Two Cards Can be Profitable
+ You do Not Need a Lot of Information Before Classifying a Player