Arcanacra http://www.yomogi.sakura.ne.jp/~si/Soli ... 04_e.shtml
Arcanacra Black Label http://www.yomogi.sakura.ne.jp/~si/Soli ... v04_e.html
Same gameplay as Cho Ren Sha 68k, its by Keim the creator of Nomltest, This is the best ive tried sofar and you actually will need some skill to master it (unlike me lol). They each have online highscore tables, but dont think you can easily get a top score due to it been a online game. MrMonkeyMan and Shoe-sama have played this before and have smashed the top scores

Uchuwars http://babarageo.com/e/2004/08/uchuwars.html one of the better mouse shooters
Nano http://games.lastchancemedia.com/nano/ more of a exercise for finger tapping then a shmup
Least Best Room http://www.asahi-net.or.jp/~cs8k-cyu/flash/lbr/ by Kento Cho, its ok but nothing special
Meteor Busters http://www.dot-invasion.com/dboy/play/i ... ?vcart=001 Nice presentation, in the style of a gameboy
The last canopy http://www.kongregate.com/games/ahbonk/the-last-canopy a pretty good mouse or keyboard shooter, quite easy to play, you can steal options from the enemy to increase your firepower.
Raiden X http://www.raidenx.net/ raiden clone it even has the purple wobbly beam!
Attack of the Meeplings http://www.tinyfrogsoftware.com/attacko ... /index.php standard shooter with bombs
Robokill Demo http://www.rocksolidarcade.com/games/robokill/ good mouse based arena shooter.
Ofc you could always play some NES games online, theres a few shooters in the libary no Recca though. http://www.virtualnes.com/