Brainwaves a two-player abstract, fairly simple in concept.
Basically, it's a grid, and you've got 3 pieces on your side, and the other guy's got three pieces on his side. To win, you have to move two of your pieces onto the other side. Your pieces are all the same shape, in red, yellow, and green. You roll a die, and then get to move one of your pieces that number.
The gimmick is this: before moving your piece, you choose which one you want to move, and then turn a hidden dial to that color. Your opponent then turns his hidden dial to the color he THINKS you're going to choose (or the color he wants to stop you from choosing).
After both players have set their dials, a button is pressed, and the colors light up, revealing the choices. If he guessed right, you don't get to move. Otherwise you do move, and then the turn alternates - your opponent rolls and you have to guess.
There are passages on the board that can be blocked strategically, and you can't pass another token - but if you land on it exactly, you send it back home
There's a lot of double- and triple- thinking ("he thinks I'm going to do that, but instead I'll do this. But what if he realizes that I know he thinks I'm going to do this...") to it, and it has a built-in balancing mechanism - when a player has gotten one piece in, he then only has two to choose from, which increases the chance of his opponent stopping him.
Most games take around 30 minutes, but with a lot of good guessing, the game could, in theory, go on forever. I've seen one game take almost an hour-and-a-half!