Discounting the graphics, Attack from Mars is probably the best freeware matching game available besides Zoo Keeper. You can select any of the 140 tiles to play with and even place your own songs in the music folder to listen to.

Tiles can be swap not only horizontally and vertically, but diagonally as well. Aliens will attempt to hamper your progress, though you can easily zap them to bits by pressing space. Use it sparingly as your zapper supply is limited.

Name: Attack from Mars
Developer: Mark Incitti
Category: Puzzle
Type: Freeware
Size: 1MB