Irem's debut shooter, R-Type, is a really special game. It has incredible art direction, really going for the overtly sexual aspects of the Giger look that most games are too cowardly to use; one of the bosses you'll be fighting is a bunch of worm penises emerging from vaginas.

It also has the "Force," an invincible option, that connects to your ship in front of or behind you; it acts as a shield, absorbing enemy fire. You can fire the Force so it floats horizontally and fires; often bosses will have a hard to reach weak area that you can fling your Force into to continue doing damage even while it's locked off from your main ship. It's a really fun addition.

However I had an insanely hard time getting through it. The game is beyond arcade difficult. I played through it with infinite credits and I'm glad I got to see it all, even though dying constantly stopped me from playing with too many of the upgrades, but it can not be overstated how difficult it is.