HuniePop/YMMV

Crosses the Line Twice: Aiko's presents all being Japanese paraphernalia, with one of Aiko's reactions being "You're so racist!" in a fit of laughter.
Game Breaker: Using these date gifts: Suede Ankle Booties, Pink Mary Janes, Compact Mirror, Sunflower, Stuffed Whale and Pearl Necklace. This can get you through pretty much any date in the game comfortably. Of course you have to get the items first, but the earlier dates are easy enough to do without the combo.
Hollywood Pudgy: Beli's 132 pounds (at 5'11"), and barely looks any bigger than any of the other girls, but she thinks of herself as overweight and often worries about her Junk Food craving.
Mexicans Love Speedy Gonzales: Nikki isn't the most flattering depiction of a typical gamer (hot bod and pretty face aside). There are also a number of typical gamers (like TotalBiscuit) that find her one of the more loveable heroines.
Narm: A good portion of the dialogue, especially from Kyu and Audrey. Kyu's introductory lines early on really set the tone for the game.
Narm Charm: Then again, the dialogue is also commonly cited as a reason for the game's popularity. It helps that only some of the characters exhibit a large amount of cheesy dialogue, while characters like Nikki and Beli are more downplayed.
Periphery Demographic: Because of the game's puzzle elements, it has developed a surprising number of straight female fans, though it is not uncommon for Dating Sims to have a female Periphery Demographic.