Sega Master System / Mark III / Game Gear
This Operation Wolf-style coin-op conversion takes you back to the gangster years of the 1930's and casts you as a copper on a mission to wipe out an evil gang.
Hoodlums pop up from all angles, and you've got to blast them using your crosshair sights before they can fire and wear down your energy bar.
The graphics are great, with plenty of neat touches, and the gameplay is very addictive. Easily one of the best shooting games on the Sega, this is well worth taking a took at.