Free game, play all you want, you never have to pay anything
Javelin
It's nice to see some kindergarten-quality artwork used in game production :) A game with one button, he-he. Click the launch button to catch the angle, then same button to fix the speed. Click, you guessed it, the launch button to throw the spear, and then, heh, the launch button to start over. Don't worry, you'll manage :D
Frozen Bubble
Once dubbed the most addictive game in the world. It was originally written for Linux and spawn a whole host of ports and clones. The rules are simple: shoot bubbles out of the cannon to form self-destructing groups of three or more. If no more bubbles left, you win. If the ceiling falls on you first, you loose.