Honorable mention to Killers... it would be #11. That being said:
10- Blood Brothers: the bass here really works as an anchor carrying that great waltz like paced 6 by 8 (or two times 3 by 4 if your prefer) tempo, filled with emotion. This is such an excellent base for the remainder of the instruments to lay upon that it's half path walked to get an excellent song.
9- For The Greater Good Of God: perhaps the most basic of all intros on this list but damn... this thing really captures the desolate atmosphere of the song's beginning (especially when Bruce starts singing) and is the the perfect launch pod for the crushing epicness that's waiting just around the corner.
8- Heaven Can Wait: the way Steve's undertones give the moto to the first riff while the guitar weeps on top of it before it all goes warp speed simply gives me goosebumps each time I listen to it. Simple yet masterfully composed.
7- Wrathchild: speaking of simple yet masterfully composed what can I say about the first notes from this old classic? Groove, intensity and one hell of a base for the song to unfold.
6- The Assassin: Another really limited array of notes in regular 4 by 4. But the way Steve arranges them makes the bass line sound absolutely stellar (in a somehow middle of the pack Maiden song).
5- Innocent Exile: another quite linear bass line yet superbly peppered with excellent groove and melody that works as the perfect kickstart for this short rocker.
4- Blood On The World's Hands: although it borrows a Geddy Lee line by the end, no one can dispute how hugely cool this intricate acoustic bass intro sounds.
3- Invaders: this song's bass is something out of this world and it starts ripping from the get go. And although being one hell of a line is far from being the best bass passage Steve pulls out here. What's not to like in Invader's bass? Ah... the chorus, of course (and not only the bass, the remainder of the composition on this damn passage is simply irritating). Other than that my favorite Maiden song when it comes to bass.
2- Infinite Dreams: it's hard to put this one at #2. Everything the bass does from the part Bruce starts singing til the song explodes in the "someone chasing" part is jaw dropping, top notch 4 string composing. Hey, it's a virtual draw with number 1 which obviously is...
1- The Clairvoyant: the way this thing starts gathering memento is utterly ground shaking. No tricks, no fanciness... Steve's bass here is focused on one thing: gathering energy in a crescendo like a tsunami forming on the background. And when the whole song explodes the effect is pure magic.