I need a fun shooter that's compatible with the OG Droid
I am sure if you install a game console emulator such as those available for GameBoy, Sega Genesis, Atari, etc.; you could find many first shooter rom games. I think there are a couple of game console emulators in the App Market.
I bet if you do a search on emulators or on my nick/handle, you can find threads with instructions and sites that have these.