These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Alternate Character Interpretation: In the Ragnarok splatbook, the Ragnarok-based adventure line (which also presumes that the Aesir are the only real pantheon) gives this to Loki. In the corebook adventure line, Loki is as evil as the Edda says. He tries to consume Surtr's heart so he can become the dominant Avatar of Muspelheim, then consume the Greater Titan of Fire from the inside out. In the Ragnarok adventure line, not so much. Indeed, his most infamous act, taking on the identity of Thokk to ensure Baldur stays dead, isn't done by him at all. It's Nana, Baldur's dead wife, who refuses to allow her husband to return to life while she must stay a ghost. However, while his presentation is different, both agree on his primary motivation which is to break free of Fate and Screw Destiny. He succeeds in the core adventure of God, but fails in Ragnarok.
Crowning Moment of Awesome: While, as in any table top RPG, awesome moments are dependent on what the players do, it should be noted that the book's example of using a Nimitz Class super-carrier as a thrown weapon probably qualifies.
Game Breaker: Some knacks come to mind. Untouchable Opponent would be the best example. With it the GM has the choice between tolerating invincible characters or overpowering the enemies that they easily kill every player without it.
Really, at Demigod levels and higher, the very existence of Epic Attributes - especially Epic Dexterity - tends to become this. When a one-point difference in a single stat means enemies that challenge one PC are often literally impossible to hit or avoid for another PC, problems tend to ensue.
God-Mode Sue: A god who invokes an Ultimate Epic Attribute or becomes an Avatar for a Purview can become one temporarily, but it costs. A god with Ultimate Strength, for example, could punch a hole in the world, while a god with Ultimate Perception can know about any event anywhere in the multiverse that involves him. Avatars are even more powerful. The Avatar of Death, for example, could wipe out a city (or a Titan) with one pass of the scythe, while the Way can go literally anywhere imaginable, instantaneously, and take an army with it when it goes. Luckily for any semblance of game balance, such feats are so monumentally expensive in Legend points that they are, at most, a once-per-story occurance, in the rarified circumstance when a player character achieves such a level of power.
Magnificent Bastard: Loki. Read the denouement of "Titanomachy" in God and then say he's not... especially when you consider that they'd been foreshadowing it ever since the first sample adventure in Hero.
Ragnarok notes that Loki is the reason they have to keep saying "Most of the Aesir" when discussing their qualities. The sidebar in which they say this is titled "That Magnificent Bastard".
Memetic Badass: The source of the Scion's (and gods and beasts') power. The more Legend Scions accumulate, the more powerful they become, until they reach the status of gods.
Moral Event Horizon: In Ragnarok, we find out that Odin has a plan set up where he will switch his mind with Vidar's at Ragnarok, saving his hide at the cost of murdering his own son. It's pointed out that this act is hideously against all the Aesir Virtues at once, managing to combine kin-slaying, oath-breaking and cowardice all in one fell swoop. Odin will actually lose all his Aesir Virtues and pick up Dark Virtues instead for doing this. What makes it even worse is that Loki actually faces up to his fated doom with more balls, and even a sense of style. When you are officially acting more chickenshit and treacherous than Loki, for the love of the Norns, it's past time to re-evaluate your life choices.
As American Gods was explicitly stated to be one of the inspirations of the game, this may be a Shout-Out. Wednesday plans to do something similar to his own son, Shadow.
In the Companion, Loki sponsored Hitler's rise to power as a way to avert Ragnarok, attempting to unite millions of people under his banner and use their ability to rewrite Fate to the Aesir's advantage. When Loki found out about the Holocaust, he was sickened. Hel made sure that the highest Nazi war criminals received the worst Underworld treatment she could provide, but oddly, Hitler never showed up...
A lot of fans hate the Yankee Pantheon the most since they include recent American figures like Uncle Sam and Paul Bunyan and still defeated the more interesting older gods. Lack of character development also makes them look like bigger Mary Sues too. At least the other European have the distinction of having interesting legendary figures like Robin Hood and D'Artagnan.
Scrappy Mechanic: Fate. Many GMs just ignore it, since it basically just promotes railroading.