i feel like i'm at a disadvantage because i keep hearing about theorem this and theorem that and i have no idea what it is, so i end up googling it to find out. let's get a comprehensive list going! (most of these assume heads up)

Baluga Theorem:
if you're raised on the turn after a flop cbet, your top pair is probably no good.
another interpretation: villains won't raise the turn on a draw (obviously will not work at higher stakes)

Yeti Theorem:
if someone is representing trips with a 3bet on the flop, they are lying.

Zeebo Theorem:
no one will fold a full house. on 777xx type boards, almost everyone will call an all in if they pair the board.

Yvesaint Theorem:
if you have 22, a 3 will flop. if you have 33, a 2 will flop. (is this for real? i found this on a 2p2 link. pretty dumb theorem (no offense to yvesaint) if you ask me.)

those are the ones i know so far, but i'm sure there's more! feel free to correct what i've already stated if it's wrong.