Brave New World - Despite the fact that this one isn't even a solid incarnation, this has to be one of the most sinister Eddies. I mean, it's a freaking cloud! Smiling evilly! That's pretty scary, and also bad***. This was my computer background for a while.
The Final Frontier - Some people disliked this redesign, I thought it was a great re-imagining of Eddie to fit the space theme. Also it was my first Maiden studio album (I had the From Fear to Eternity "best of" before it) (I know, I'm a noob), so it kinda has that special quality for me in that when I first got this album it was a very intimidating cover.
Seventh Son of a Seventh Son cover - What a truly strange image! Not much was left of Ed at this point, but he was still VERY intimidating. Also, it took me awhile before I noticed what he was holding… Alarming.
Powerslave - Eddie as a pharaoh. Just an awesome concept, taking Eddie back to ancient Egypt, and making him a pharaoh who is revered as a god. Also pretty symbolic of Maiden's status to a lot of fans by that point
Reincarnation of Benjamin Breeg - This song captured my imagination (and I actually first found this forum searching for the identity of Breeg), and seeing this cover was yet another mystery in the story of the character in this song. Why is Eddie digging his grave? And why does he look so… tortured? The mystery of it is why I love this Eddie.
Live After Death - Eddie is clawing himself out of the ground while being brought to life by lightning. Need more be said?
Of course, I love a whole lot more Eddies, but these are a few favorites.