Tetrix

Tetrix is a competently designed and decent looking Tetris game. Its main distinguishing feature is that two players can play against each other in a competitive mode, sharing the same keyboard. Different blocks fall for each player, so the winner is somewhat up to chance. Other than that, things are pretty usual for a Tetris game. The author has released the full version for free. Also there is a bonus game included, Tank vs UFO, which is an updated version of the first game the author ever coded.

This is the same game as Tetrix, which has the full page.