When playing Castlevania there are 2 tricks I almost always use. And I've been looking for others like them.
The 1st is the Holy Water. It's completely fucking broken. If you pick it up in level 2 and can hold on to it for the rest of the game, every boss is a cake walk. Cause it pauses their sprite where they stand. Since they can't move, you just spam the piss out of it and = WIN! Of course it's not 100% guaranteed to win you the game. Because you still need to know enemy patterns, level layout and killing Frankenstein and Death with it takes some really good timing.
The second is a minor glitch. When you are in level 2 of the game. You can skip a bit of platforming and Medusa heads if you jump where I have circled. If you jump and let a Medusa hit you, you'll get knocked back. But rather than falling in the pit, you'll actually fly up and land on the upper ledge. Allowing you to pretty much skip the whole room. Just make sure you are facing right, so it knocks you left and you're golden.