Polyominoes by quickcup is indeed the one millionth Tetris clone known to man. However, it features unique modes and for being a homebrew it is fairly complete.

4 unique modes of game play
3 different sets of shapes to play with
menus and presentation
artificial intelligence
2 player link play (not fully tested)
many options
sound, music, and special effects

See the instructions in the zip for more detailed documentation.

Thanks to PDroms for the news