Well, though I'm sorry for stealing the Philosophus's thunder (of course, how sorry can I be if I'm posting this anyway), I still feel that this little NES gem deserves a look.
Nowadays, genre-blending games are something of a plague. Like frankenstein's monster, they are abominations of anture stitched together and brought to life by means best kept secret from the world, lest it be driven mad. Only a few games that blend two types of gameplay are, indeed, worth looking into. Others may include different gameplay mechanics as a token minigame, thus ensuring that they don't foul up the rest of the game.
The first successful genre-blender, however, was The Guardian Legend. Even though it was cursed with bad box art (American version only), it still turned out to be one of the high points of NES gaming. The story is simple enough: A huge planetoid worldship filled with a cargo of nasty aliens and belligerent military hardware is headed straight for Earth, and your job, as a transfromable android combatant (female, in the Japanese tradition), has to find some way of getting the thing to explode before Earth gets roasted.
It begins simply enough, as a top-down shooter with the difference that your carft was built by designers who decided that armoring a space fighter with crepe-paper wasn't going to cut it. As soon as one clears that first level, however, the player will find that the fighter had now transformed into humanoid girl form, and the controls switch to a more zelda-like construction. Except, of course, that the Guardian can walk and shoot diagonally. Thus, the game is divided into two types of play: the top-down shooter, and the zelda-like overworld. Most special weapons can be used in either section, including, oddly enough, the beam swords. Special weapons require ammo, which is plentiful enough. There are two quirks associated with special weapons, however:
1.) When you have a special weapon equipped, the number of normal shots you can have on the screen at once is reduced, depending on the weapon, and:
2.) The more special weapon ammo you have, the wider the area of effect of your normal shot.
Plainly put, the overworld is big. It's at least twice as big as in the original Legend of zelda, and with bosses of its own. There are also a grand total of 22 shooter levels, so only marathon gamers should try this in one sitting. If there is one complaint I have about the game, is that it still used the password system (though not nearly as bad as the one in the original River City Ransom), thus rendering cumbersome to record progress.The difficulty of the game, once one passes a certain poijnt, expands at a geometric rate, thus ensuring that you'll explore all of the overworld looking for that powerup that will help you not die against the next shooter boss. Still, though, it's not an unfair game: I can beat the thing, after all.
Unfortunately, Compile is no longer around to make shooters like these, and they do have so many worth looking at. Next time, however, huge battleships approach fast: A look at Darius.