Mitigo9
Mitigo 9 is an old school, side scroll shooter, where the player has to fight against enemy ships, giant insects, tanks, robots and more. To help the player in this mission, there are twelve different upgrades, which can be combined in lots of different ways. ... You'll see action in different locations like space, forests, deserts, ruined cities, asteroids and more!
http://iluminategames.com/demo/Mitigo9Demo%20Setup.exe - 16Mb - Download - Screenshot

Cosmic Defender
Based on a classic arcade retro game, this side scrolling shooter is pure addictive endless fun. Destroy the invading aliens and save your brethren from abduction. Compete against other players via the Internet high score board. Free game with no spyware brought to you by 2DPlay.
http://www.2dplay.com/cosmic-defender/CosmicDefenderSetup.exe - 891Kb - Download - Screenshot

Alien Stars
Welcome to the fantastic world of Alien Stars - a breathtaking vertical scrolling space shooter game! The game of our future. Leave your fears behind. Set your mind free. Believe in the endless universe and the millions of alien galaxies.
http://www.awem.com/download/AlienStarsSetup.exe - 11Mb - Download - Screenshot

Note shooter
Listen and recognize note free online music ear training game. Online music lesson for all standards and styles of musician are available all over the net. Some sites offer these to encourage you to purchase their services, products or to enhance their site and they're free!
http://www.ababasoft.com/music/noteshooter.zip - 50Kb - Download - Screenshot

Atomaders
This space-shooter is based upon the classical Invaders/Galaxian idea. You have to liberate your planet system from the alien invasion using your spacefighter. Player can obtain various extra-weapons and special abilities by destroying enemy cyborgs, fighters and motherships. ... Additional planet systems could be downloaded from the Internet. ... Each planet has its own cyborg types and an unique powerful boss at the last level.
http://kraisoft.com/files/atomadersdemo.exe - 9Mb - Download - Screenshot

TapzMania
TapzMania is a shooter game where you must defend the plants from the hungry bugs. Don't let them aproach the plants otherwise they will die! Old classic PSSST! gone 3D. TapzMania features: # 300 levels (up to 1600 through expansions). # 5 skill levels. ... # Multiplayer mode (via Bluetooth). ... # Online scoreboard. ... # Built in tutorial. ... # 3 environments (up to 16 through expansions).
http://www.ru0-games.com/files/tapzmania.zip - 684Kb - Download - Screenshot

Alien Invaders Attack!
Free arcade style space shooter game for the PC.
http://www.sci-fi-game.com/download/aia.exe - 4Mb - Download - Screenshot

Space Alien Invaders
Free arcade style space shooter game for the PC.
http://www.freewareshareware.net/download/sai.exe - 1Mb - Download - Screenshot

After The End
Cut your way through locations filled with mutants in this 3rd person 3D-shooter. In your attempt of getting replacement units for your dropship and discovering the source of the evil raging all over the planet you will fight dreadful creatures with your arsenal of weaponry and special abilities. ... Nice 3D graphics and sound FX, 16 weapons and devices, 3 game modes (Campaign, Firing range, Survival), Worldwide Hall of Fame and much more.
http://kraisoft.com/files/aftertheenddemo.exe - 16Mb - Download - Screenshot

Bad Folkers!
Big Weapons, Big Enemies, Big-Mouthed Pilot! Based on the old "German Fokkers" joke, this is the hilarious shooter game where your pilot yells and hollers so you don't have to! One of the funniest games you'll ever play! And of course it has the standard and not-so-standard superweapons and big...
http://www.senatorgames.com/sengames/folkers/badfolk.exe - 9Mb - Download - Screenshot