A7xpg and Parsec47 are two more superb "abstract shooters" from Kenta Cho, prolific Japanese freeware developer.

Core Design's computer conversion of SEGA's top-down shoot'em up Action Fighter for the Sega Master System and Mega Drive.

AeroStyle is an excellent freeform aerial combat shooter that sports a very intuitive mouse-driven interface, crisp SVGA graphics, and fun gameplay.

Afterburner 3D is an excellent fanmade remake of SEGA's classic first-person shooter Afterburner.

Air is an excellent side-scroller from premier Taiwan developer Softstar.

Airlift Rescue is a fun variation of the classic Chopper game of yore in which, manning artillery, you must shoot all enemies that drop from parachutes before they get close...

A solid conversion of a little-known Konami arcade game of the same name, Ajax is a challenging vertical scrolling shoot-em-up for one or two players.

Amanagi is an excellent horizontal shooter from Japan that boasts excellent 3D graphics and gameplay.

Ambush in Sector 9 is a great "retro" style shooter from Pug Fugly Games, programmed in Game Maker.

One of the most impressive freeware shooters I played, Another Zero is also one of the most difficult games in the genre, freeware or not.