It seems more than appropriate to make this list's number one entry harken back to one of the tracks that started it all. The final entry on their self-titled debut, "Iron Maiden" is a song that perfectly summarises the band's early, game-changing aspirations through one, now-infamous refrain: "Wherever you are, Iron Maiden's gonna get ya, no matter how far."
However, the song also has fun with its title, at numerous times drawing reference to the medieval torture device from which Maiden took its name. With lines like "See the blood begin to flow as it falls upon the floor," this is hardly surprising for die-hard fans.
But what may be more intriguing and unknown is that the song's writer, Steve Harris, has since hinted that there could be even further meaning behind the track. He has mused that the term "iron maiden" could also be used more literally and refer to a cold-hearted woman, hence lyrics like "Won't you come into my room? I wanna show you all my wares," which combine with the song's violent imagery to suggest something of a Black Widow-style seductress.
This third reading also opens up a fourth possibility in turn. Followers of very early Maiden will know that they weren't exactly fans of Margaret Thatcher, infamously having Eddie kill her on the cover of their 7" "Sanctuary" single. (Thatcher would later get her revenge on Eddie by attempting to shoot him on the "Women in Uniform" artwork.)
And take a guess what one of Thatcher's nicknames was. The Iron Maiden.
While the Thatcher interpretation doesn't seem to have ever been confirmed by the band, it's difficult to imagine them not taking the chance to again slander the then-Prime Minister after they, you know... had her killed by their mascot that one time.
Overall, this means "Iron Maiden" (despite its initially simple and violent lyrics) seems to have far, far more going on than anybody gave it credit for. And with the band that it took its name from going on to be one of the biggest pioneers in all of rock, this was definitely an early sign of their undisputed genius.