Let's start a chat about concepts, ideas, and designs for custom enemies that can be made using the enemy editor. The only rule here is that enemies can NOT be scripted. Other than that, have it.
My own ideas:
Death Zol: These cause high damage when touched. They move much faster than your typical Zol, maybe 150 as their step rate? They still stop at every tile though, a trademark of the Zol breed. What makes them really unique though is that if you don't kill them quickly enough, they tribble into a puddle-like phase that has a step speed of 300, which after a second or so tribbles into TWO more Death Zols. The process can repeat indefinitely if you can't manage to kill so you could soon find yourself in a room full of these. As for its HP, not sure but I'd say probably about 3 or 4 hits to kill with the white sword.
Fire Vire: This enemy certainly lives up to its rhyming name in that it hops around the screen, as vires do, and spawns a ring of fire as it's doing so. When killed, it splits into 3 red Keese. Pretty dangerous enemies, especially in large numbers.
Shielded Goriyas: Exactly like it sounds. You could draw a shield sprite over the existing red/blue goriyas & make copies of each and check the "shielded from the front" box. If you want, you can make a silver shield kind whose shield can be broken and a golden shield whose shield cannot be broken. In fact, you could do this for a lot of walking enemies.
Poison Darknut: A green or perhaps purple darknut that has a speed somewhere between the red & the blue's speed, does only 1 full heart of damage but when touched, causes a sword and/or item jinx.
Monshroom (and Toxic Cloud): A monstrous mushroom! This is a walking enemy that spawns another "enemy", the Toxic Cloud. The Cloud is then a tribble enemy that after a period of time (maybe like 5 - 6 seconds?) then tribbles into nothing (in other words, it fades away). The cloud doesn't deal damage but causes temporary sword/item jinx.
Vampire Darknut: A darknut that if you don't kill too quickly, it will tribble into a keese or bat which flies around really fast and has a higher HP than your typical keese or bat. Then the bat will tribble back into the vampire darknut. So really it tribbles back and forth and you must kill it in either form quick enough otherwise it will tribble, thereby regaining its HP.
Skulls: These have extremely high HP, like 99, so they take forever to kill with low-power weapons such as the sword, however, they are an insta-kill with the hammer. So they're annoying up until you find that weapon, then they're a breeze. They move really slow. There are three types, each with different colored eyes: Red: Takes you health (does damage) Green: Takes your magic Yellow: Takes your rupees