Jordan Neidlinger released a Tic Tac Toe game for the PSP. Release notes:

Coding Tic-Tac-Toe is my first project on the PSP, and as such I chose it because of its simplicity. Coding the game honed by somewhat rusty coding skills, and gave me knowledge and know how with PSP-homebrew’s. I know its not a fancy game, nor is it anything special, but I had fun making it, so I thought I might as well release it!

Note: The AI in this game is almost non-existence RIGHT NOW. I only put in the simplest of computer thinking, if you would even call it that. If you cant win everytime, SHAMEON YOU! (just kidding).