These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Anticlimax Boss: Astaroth. Even when you're stuck with the shield, he's still a cakewalk compared to the level you had to go through to reach him.
Demonic Spiders: Pretty much everything in the game, but especially Red Arremer. Those things stay up in the air where you can't hit them until they swoop down at you and are absolute hell to avoid because they are MUCH faster than you are.
Scrappy Mechanic: Needing the shield to enter the boss fight in Level 6, otherwise you have to restart Level 5. The bad part of this is that the shield is a terrible weapon, while it blocks projectiles it hits, it has shorter range than the knife and the lance and a lower fire rate than the knife. If you die and have to restart Level 6 with the shield, you're dead.
Scrappy Weapon: The fire, you'll never hit anything with it and if two fireballs are thrown you have to wait for the fire to die down before you attack again.
The hatchet is even worse. It flies in the same arc as the torch, but it also passes through enemies and walls. While this may make it useful in dealing with groups of smaller enemies, it is a death sentence against enemies that take multiple hits to kill (such as the ogres in stage 2), as you'll never be able to fire quickly enough to defeat them before they kill you.
Woolseyism: In the NES Version the cross in the Japanese version is changed to a shield in the Western release. Although the shield still has an image of a cross on it.