Kyle XY/YMMV

Anvilicious: "Free To Be You And Me", which delivered a rather heavy-handed Aesop about homosexuality, including having all the main characters organise an alternative school dance for gays and lesbians to go to, having Josh learn a valuable lesson and having Jerkass Charlie behave homophobically.
Complete Monster: Cassidy in Season 3, after the revelation he killed Sarah and his actions in the finale.
Crowning Moment of Awesome: In Season 3, Kyle upercutting Cassidy with enough force to send him flying out of the house.
Crowning Moment of Heartwarming: Also in Season 3, the revelation that Sarah never left Jessi after all.
Germans Love David Hasselhoff: Kyle XY gets more love in Spain than he does in the States. With an average of three million viewers per episode in Spain (huge in European TV), this show remains a fundamental program for its broadcaster.
Ho Yay Shipping: Kyle and Declan (dubbed in-universe as "Keclan" by Hillary). When the two have a falling out in Season 2, people speak about it as if they had broken up.
Mary Sue: Kyle. Borders on Deconstruction, as most of the characters are well aware of Kyle's utter perfection, and one character got him drunk just because he wanted to see if Kyle had any flaws. It still doesn't work.
- Also counts as an example of Tropes Are Not Bad, since Kyle's Mary Sueness is a major plot point and the raison d'etre of the entire series.
- And again, a deconstruction of the ideal 'perfect son'. The other teenagers are depicted as heavily flawed, but not without their good points. Despite Kyle's so-called utter flawlessness, the show goes to great lengths, particularly during the first half of season one, to demonstrate that raising someone like Kyle is no easy task.
Seasonal Rot: Season 2 was the weak link in the series, spending more time on the tangled mass of love triangles and teen relationships than Kyle himself, and failing to provide a major villain. It got better by the time of Season 3, which is probably the best season in the series.
Ship-to-Ship Combat (Just go onto the boards and be prepared to be met with tons of threads documenting the all out war between the Kyle/Amanda shippers and the Kyle/Jessi shippers)
Too Good to Last: Season 3 was probably the best season in the entire series, but low viewer ratings led to the series being cancelled nonetheless.
Unintentionally Sympathetic: A surprisingly large amount of the villains. Aside from the blatant Big Bads like Thatcher and Valentine, most of the antagonists are Punch Clock Villains who express their distaste with having to pursue or manipulate teenagers.
Wangst: Amanda's whining about Kyle got really annoying, but it wasn't as if the tropers who thought this were sad to see her breakup with Kyle.
Woobie: Kyle in Season 1, and even after that. Contrast with Jessi, who is a Woobie, Destroyer of Worlds.