Rescue by Stern... Think Robotron in a helicopter. Great game you rarely hear anyone talk about.
Wow, I thought I was the only one on earth who appreciated this game--glad to see I'm not. Very fun. There is another game by Stern called "Minefield" which must have run on the same hardware because it's essentially the same game, only you're a vehicle on the ground rather than a chopper. I just found it by accident a few days ago, actually.
A few other token mentions of various genres:
Pandora's Palace (single screen platformer). It owes a lot to Donkey Kong but very addictive.
Megatack (slide n' shoot space game). Nice difficulty ramp--not overly frustrating. It almost has the soul of an Atari 2600 game.
Metro-Cross (side-scrolling runner). If this game was called "Super Space Pitfall!" it would fit.
Block Hole (puzzle). Ok, insert joke here. Very addictive puzzler. I recently played a cool version of this on Gameboy, but it was called "Quarth".
Snow Bros. (single screen co-op platformer). Totally cops Bubble Bobble, the main difference being it doesn't suck.
Armored Car (maze). Probably owes a bit to Rally X, but I like this better.
Kickle Cubele (??). Not sure what you'd classify this as, but it's kind of like Pengo but with puzzle elements. Very addictive. It was called "Kickle Cubicle" on the NES. I think it is actually a Japanese arcade title called "Meikyu Jima", and got the bastardized "Cubele" name when it was bootlegged in the US, but not sure.