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.
Arc Fatigue: The amnesia storyline, which was finally resolved at the end of season 2. Monroe went on to apologize for it during season 3.
Big Lipped Alligator Moment: So far, Renard's nightmare about Juliette appearing in his bedroom and turning into a hag in "Nameless" has yet to be explained or even referred to.
The title theme starting from Season Two. They tried to tack on an awkward narration when it was introduced, but once the narration was taken away it was AWESOME.
Designated Protagonist Syndrome: A common critique of the show is that Nick is just not interesting, and the Monster of the Week format doesn't give him much opportunity to become so, as it inevitably involves him calling Monroe in to explain what's happening and overshadow him.
The writer's seem to have realized this, and for several episodes have taken the focus off of Monroe to allow for more character development and differentiation for Nick, who has gone from a typical cop-show protagonist to become more pragmatic and snarky, as well as coming into his own new identity as a Grimm/Cop.
Some fans consider this a strength of the show, since it is a nice reprieve from all the "special" or "tortured" protagonists which are especially common in Genre show. Nick being a normal boring person who deals with his new abilities without a lot of drama is one of the aspects which sets the show apart.
Eric Renard is quite dashing, when he's not having people tortured or killed.
Khloe Sedgwick, the Musai from "Kiss of the Muse," professes that what the men who fall in love with her do (obsession with her, violent rage towards any challengers for her love) is not her fault, but over the course of the episode it becomes clear she both encourages it and seems to enjoy watching it
Fan-Preferred Couple: Nick/Monroe and Nick/Renard. Nick/Ariel and Nick/Adalind are not as popular as the two previously mentioned ships, but they do seem to receive more enthusiasm from fans than the currently-not-together Official Couple Nick/Juliette and are gradually gaining more popularity.
Genius Bonus: More like paying attention bonus, but Monroe brings up during Season 2 that he found his grandmother's antique picnic basket. What kind of wesen is Monroe again, and what well-known fairytale did one of those and someone with a basket feature in?
Nick calls Rosalee when he needs help with a Wesen medical issue. Monroe is jealous that Nick didn't call him.
When Nick and Monroe are talking about how they have to lie about their entire friendship to Juliette, it sounds more like they're talking about covering up an affair rather than hiding their supernatural natures.
Adalind is, however, a Magnificent Bitch...maybe. Recent events may revert her to her old ways.
Narm: When Adalind meets Frau Pesche, probably intended, at least for the weirdness.
Frau Pesche: I knew your mother well.
Adalind: Me too.
Although, the tone of conversation suggested that Adalind was really not sorry to see her mother go and really wanted Frau Pesche to stop talking about it.
Each and every time captain Renard is talking German. The man grew up in Austria, you'd expect him to get the syntax right, at least. Same goes for most other instances of characters speaking German, although Monroe is excused for being a third generation immigrant.
We don't know how much time Renard spent in Austria. He went to school in Switzerland (a French-speaking nation) and his mother is French-speaking. It makes sense that French is his stronger language. Also note that he and his brother spoke to each other in French, not German.
One-Scene Wonder: Many side-characters like Hap, Roddy, Barry, Holly, and Bud The Fridge Repairman have gained following.
Valentina Espinosa and Ian Harmon were nowhere near them, but in way of growing into it.
Casey, a would-be victim in "Mr. Sandman". She actually does some pretty Genre Savvy things like covering her eyes against a wesen that targets them when he attacks her, gets a weapon as soon as she's able to, and ultimately is the one to defeat the wesen of the week.
This sticks hard for Juliette, and not so much for Hank (at first). Although Juliette could still rapidly head back to Scrappy territory. Actually, while many people love it, some people are complaining about the amnesia storyline, and, despite her good amount of fan love, some people are claiming Bitsie Tulloch is the weakest cast member.
Finally achieved for Hank "One Punch" Griffin in in Bad Moon Rising when he goes from freaking out over finding out about the Wesen - and that his goddaughter and best friend are one - to dropping a Coyotl (in full game face, no less) in one punch!
Romantic Plot Tumor: The Nick-Juliet-Renard love triangle could be seen as this untill season 2 episode 13, when it becomes Fridge Brilliance by resolving another plot while developing.
The Scrappy: Adalind, for some time untill the penultimate episode she appeared in in season 1 showed that she had a Stage Mom and was a Love Martyr to Renard. That, Renard's Manipulative Bastard-ness and her elegant and carefully-thought revenge increased her popularity, though even her new fans find her annoying. However, her vile intentions towards her own unborn child are probably not going to help people's opinions of her.
Juliette's been wavering in and out of this trope, but seems to have been rescued from it, albeit on a special way.
The actress playing "Mrs. Garcia" in "El Cucuy" is 54◊. Mrs. Garcia is 77, and the costuming department thought that the way they could age her up was giving her a ridiculous, cheap-looking wig◊. It looks worse in the episode - it looks unnatural and you can almost see where the wig ends and her real hair begins!
Squick:The less said about the frogs in "Lonelyhearts", the better. Or the rats in "Danse Macabre" who chewed off a man's face. Or the judge with a gavel shoved down his throat and the woman with her tongue cut out in "Game Ogre".
How Spinnetods kill their victims.
Not as bad as some other examples, but two words: Blood. Cookies.
Basically, if you're going to get killed by a wesen who isn't concerned about The Masquerade at the moment or you're bumping into a wesen engaged in some of the more instinctual habits... it's probably not going to particularly nice.
What Geiers are infamous for as a species - brutally harvesting human organs from victims that are still alive, be they wounded soldiers on the battlefield or homeless kids on the streets - and selling them on a Wessen black market that uses the parts like apothecary ingredients.
The Lowen underground gladiator ring feeding new contestants the remains of defeated fighters.
Let's also not forget how traditional Coyotl families "introduce" seventeen-year old female members to the pack. Which is not an introduction and just a way to sugar-coat gang-rape and incest.
Also in "To Protect and Serve", Nick falls into a pit of decomposed corpses. When trying to find his flashlight, he accidentally grabs rotten body parts.
In "Mr. Sandman" we get the image of a parasitic worm wriggling out of a persons bloody eye socket. Sleep well.
A pregnant Gluhenvolk's "pickles and ice cream" is apparently raw cow ovaries. Yum.
The hideous fate of Blutbaden who ate the "Black Despair" mushrooms in "Best Served Cold". Their helplessness and hopelessness are as horrible as their agony.
Tastes Like Diabetes: In "The Bottle Imp", the foster family that April is sent to live with have shades of this. The audience is not surprised when after five minutes of dealing with them, she puts on her Game Face and attacks.
Tear Jerker: Angelina's death and Monroe's grieving for her.
The family in "Bears Will Be Bears" has a lot of indigenous culture artifacts in their home. The wife is very devoted to the idea of respecting ancestors, to the point of letting her son do a violent and outdated ritual for their kind. And then, the father (who didn't know until it almost ended badly), who is white, says to Nick:
“It isn’t easy to have to give up your history. You’ve never had to give up yours.”
Averted in "La Llorona". Despite a majority of the characters in the episode being Hispanic and the main victim even only speaking Spanish, never are they treated as potential border hoppers or otherwise suggested to be anything other than US citizens. Or in the case of the special guest star - who has a strong accent - another police officer from the US.
"Nameless" features a female game programmer who apparently did not write the innovative code for her game. Said female also blows off the person who helped her and it's suggested she Really Gets Around. While this is all well and dandy for any other situation, considering the relative lack of females in the game industry, much less female programmers, as well as the very much macho/boys club culture of the industry, this kind of portrayal only reinforces the anti-female attitude in the industry/diminishes legitimately great female game devs and female technical experts in any field.
What an Idiot: It's probably not such a good idea for Adalind to be letting so many people know she's carrying Royal blood. Or for her to to trust Stefania so completely since the latter has already shown backstabbing tendencies.
Monroe, at times, especially in "Three Bad Wolves," as well as Hap. Hap gets killed over a family feud he was never involved in while Monroe is caught between looking for vengeance of his friends death and staying out of the fight to avoid escalating things to worse levels... even though that means the woman he loves may end up dead.