Operation Spacehog  
I found problem with some resolution : at 1440x900 i don't see the top menu with power-up, at 1920x1200 the screen is too small. Great power-up system (Gradius style) and Intro system. Graphics non-innovative. One of the most complete game of Allegro Community

Happyland Adventures - Xmas Edition  
This is one of the best free-platform game to download, it's very professional with great level design (some tricky quest are very ingenious), relaxing music during play, controls are very smooth , graphics is simple but very stylish. I play and finish the game in one week I enjoyed with this one.

Saucelifter  
The gameplay is very good and controls are smooth and accurate. I like the graphics specially the particle effect. I don't the difficulty level because it grows too fast after first round. But this remains a great allegro game.