My top 10. Missing some of the obvious ones because I've never played with them, so they aren't on my list.
1.) Storm Crow: Easily the greatest creature in magic. An efficient beater that can't be pinged to death. Flies over Tarmogoyf and Confidant. Since your playing blue you'll have counter-magic to protect him from any serious threats. By the the time you resolve Meloku, you'll be taking 4 damage a turn from an army of crows. And crows block illusion tokens all day long without dying. And he's automatically better than any other non-blue creature because he can be pitched to Force of Will. Finally, better than Tempest Owl since he can never be countered by Ertai's Treachery and he gets pumped by Muranga Petragylphs if Gravity Bind is in play.
2.) Nicol Bolas: Yes, he's expensive, under powered for his cost and has an upkeep. But when your using fun methods to bring out creatures (i.e. reanimation or things like Dragon Arch) there's very few who'd scoff at a 7/7 flier that almost guarantees you victory when it connects with an opponent's face.
3.) Lin Sivvi, Defiant Hero: The only banned legendary creature in Magic for a reason. She was stronger with the old legendary rule as playing her first meant your opponent could never play her. She searches for an infinite combo all by herself (Standing Troop + Outrider en-Kor) making her killer in EDH. In regular play...she is just a tool box in a single card that can also be searched for by many members of that tool box. How cool is that? Plus, almost impossible to mill a Lin Sivvi player.
4.) Zodiac Dragon: Honorable mentions here for being a $200 card just because its original wording let you go infinite with cards like Wild Mongrel (and for being in the hard to get P3K set). Honestly its a really bad card by today's gathering/oracle wording. Yet its worth the same price as a playset of Goyfs.
5.) Avatar of Woe: Besides being the strongest Preconstructed deck card since Limited Resources and until Umezawa's Jitte, Avatar of Woe is a nightmare. Evasion. Big body. Easy to achieve alternate cost. And removal. All in one body with amazing art by RK Post.
6.) Painter's Servant: How is this not on any lists? This guy is totally bonkers. Besides being insane with Iona and Defense of the Heart, its also one of the only creatures (aside from Recruiter, only used to tutor this guy) played in modern Vintage-combo decks. On top of that he is the only card in magic to modify cards in every zone--meaning he changes the color of Planar cards making for some interesting game interactions (Circles of Protection...).
7.) Shield Sphere: I'm still stunned when people mention Phyrexian Walker as a blocker. If you look up "underrated" in the dictionary, you'll find a picture of Shield Sphere.
8.) Baron Sengir: I don't care if his regeneration effect can and will never hit myself. I don't care if his +2/+2 counter ability is ultimately useless as no one will swing into him or even block him without an in-hand "out". He is the true lord of the Vampires and the only reason to ever crack a pack of homelands once Autumn Willow and Ishan's Shade got outclassed...and Merchant Scroll got reprinted. Mostly for the Pete Venters artwork I think.
9.) Lhurgoyf: Even if you don't see it as the most game warping creature of its era for its amazing potential at mid-end game power at such a relatively low mana cost, no one can deny how memorable its flavor-text is.
10.) Spirit of the Night: The original "Akroma". Defined itself as the winning beat-stick of Brian Seldon's MI-TE block pro tour winning Survival-Recurring deck. The strongest creature to date only to be out-matched by (arguably) Masticore and Morphling. Really wasn't truly outmatched in terms of raw power until Akroma herself (in my opinion).
Runner Ups: Blinding Angel (for limited), Ertai (from tempest block; for annoyance), Squee (Zodiac Dragon won for its old wording), White Knight (for managing to stay a competitive creature and card from Alpha till now whereas every other creature from the set, save maybe for its twin and hypnotic specter, has been hopelessly outclassed) and Phage (combo with Volrath's Shapeshifter; and for being the best side-deck card against Telemin Performance)
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A land that wins you the game if you control 10 gates.
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Stasis versus Helix Pinnacle
Will the power of Chronatog+Rootmaze+Stasis mill beat Helix Pinnacle + Forsaken City?!
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1.) Storm Crow: Easily the greatest creature in magic. An efficient beater that can't be pinged to death. Flies over Tarmogoyf and Confidant. Since your playing blue you'll have counter-magic to protect him from any serious threats. By the the time you resolve Meloku, you'll be taking 4 damage a turn from an army of crows. And crows block illusion tokens all day long without dying. And he's automatically better than any other non-blue creature because he can be pitched to Force of Will. Finally, better than Tempest Owl since he can never be countered by Ertai's Treachery and he gets pumped by Muranga Petragylphs if Gravity Bind is in play.
2.) Nicol Bolas: Yes, he's expensive, under powered for his cost and has an upkeep. But when your using fun methods to bring out creatures (i.e. reanimation or things like Dragon Arch) there's very few who'd scoff at a 7/7 flier that almost guarantees you victory when it connects with an opponent's face.
3.) Lin Sivvi, Defiant Hero: The only banned legendary creature in Magic for a reason. She was stronger with the old legendary rule as playing her first meant your opponent could never play her. She searches for an infinite combo all by herself (Standing Troop + Outrider en-Kor) making her killer in EDH. In regular play...she is just a tool box in a single card that can also be searched for by many members of that tool box. How cool is that? Plus, almost impossible to mill a Lin Sivvi player.
4.) Zodiac Dragon: Honorable mentions here for being a $200 card just because its original wording let you go infinite with cards like Wild Mongrel (and for being in the hard to get P3K set). Honestly its a really bad card by today's gathering/oracle wording. Yet its worth the same price as a playset of Goyfs.
5.) Avatar of Woe: Besides being the strongest Preconstructed deck card since Limited Resources and until Umezawa's Jitte, Avatar of Woe is a nightmare. Evasion. Big body. Easy to achieve alternate cost. And removal. All in one body with amazing art by RK Post.
6.) Painter's Servant: How is this not on any lists? This guy is totally bonkers. Besides being insane with Iona and Defense of the Heart, its also one of the only creatures (aside from Recruiter, only used to tutor this guy) played in modern Vintage-combo decks. On top of that he is the only card in magic to modify cards in every zone--meaning he changes the color of Planar cards making for some interesting game interactions (Circles of Protection...).
7.) Shield Sphere: I'm still stunned when people mention Phyrexian Walker as a blocker. If you look up "underrated" in the dictionary, you'll find a picture of Shield Sphere.
8.) Baron Sengir: I don't care if his regeneration effect can and will never hit myself. I don't care if his +2/+2 counter ability is ultimately useless as no one will swing into him or even block him without an in-hand "out". He is the true lord of the Vampires and the only reason to ever crack a pack of homelands once Autumn Willow and Ishan's Shade got outclassed...and Merchant Scroll got reprinted. Mostly for the Pete Venters artwork I think.
9.) Lhurgoyf: Even if you don't see it as the most game warping creature of its era for its amazing potential at mid-end game power at such a relatively low mana cost, no one can deny how memorable its flavor-text is.
10.) Spirit of the Night: The original "Akroma". Defined itself as the winning beat-stick of Brian Seldon's MI-TE block pro tour winning Survival-Recurring deck. The strongest creature to date only to be out-matched by (arguably) Masticore and Morphling. Really wasn't truly outmatched in terms of raw power until Akroma herself (in my opinion).
Runner Ups: Blinding Angel (for limited), Ertai (from tempest block; for annoyance), Squee (Zodiac Dragon won for its old wording), White Knight (for managing to stay a competitive creature and card from Alpha till now whereas every other creature from the set, save maybe for its twin and hypnotic specter, has been hopelessly outclassed) and Phage (combo with Volrath's Shapeshifter; and for being the best side-deck card against Telemin Performance)