Tic Tac Toe (by Maurice Quennet) for Ti-83 (and 83+ should work too)
(there is a ingame instruction)
This is a classic tictactoe game with a one player and a one-calc 2 player mode. the 1 player mode has 4 difficulties and
u can choose if u start ore the computer. u r always X and the computer is always O. to draw ur X or O use the numbers 1-9 like this:
7|8|9
4|5|6
1|2|3
In 2 player mode both players have to use the numbers 1-9. they play by turns.
use the button CLEAR during a game (in both modes) to get to the main menu. pressing MODE will quit the game 
immediately (in both modes too).
the game recognizes who wins and if the game is undecided. game game is only undecided if the field is full and no player
has three in a row. 
NEWNEWNEWNEWNEWNEWNEWNEWNEWNEW:
size reduced from 8kb to 5.5kb
+ AI should not stuck anymore (SHOULD I havent tested yet)

im sorry for any language fault