EASER  I used to love the game Space Junkie in the pre-OS X days. Alas, that game is gone forever now that I can't run Classic. But Titan Attacks has given me pretty much the same enjoyment; it's the best of its kind that I've found. My wish is that the screen could be resized by dragging a corner. My only two options are full screen or tiny screen. I don't like full-screen games, so I'm stuck with tiny screen. Even a medium-sized screen would be appreciated. But on the whole, it's good, and I plan to buy this next payday.  
(Version 1.7)

MACEVANGELIST  This is a great game for everyone who enjoyed Space Invaders back in the 1980s.

One of the more entertaining games with an online highscore list.

DO NOT PLAY THIS GAME IF YOU HAVE A JOB AND CAN'T STOP PLAYING UNTIL YOU MAKE IT FIRST ON THE HIGHSCORE LIST.

Actually I wished that feature could be turned off because you tend to be obsessed about beating someone's record rather than just enjoy a little distraction. (-1 point in features)

Each level is followed by a list of items to buy. If you earned enough money shooting space ships or collecting special items (dropped bonuses, bailing aliens, destroying falling wrecks) you can choose power ups for shield, gun power, extra bullets, smartbombs, addons or ship speed.

Full-screen mode with a resolution switch is possible and does not relocate windows or desktop icons when you leave it. Aspect ratio stays 4:3 even on 16:10 displays. (-1 point for graphics & sound then)

Controls, music volume and effects volume are configurable.  
(Version 1.1)