Good and decent shows that were cancelled:
- Justice League - Only aired the episodes of the last season once, and never reran them
- Megas XLR - Was open for another season, but executives failed to understand the shows humor
- Teen Titans - The audience "skewed too old" for the networks liking, it ended on a cliffhanger
- The Life and Times of Juniper Lee - Screwed around with the timeslot, didn't air the series last few episodes
- The Secret Saturdays - Screwed around with the timeslot, aired new episodes in the slot reruns were usually aired (8:30 AM on Sunday mornings), ended on a cliffhanger if I remember right
- Fosters Home For Imaginary Friends - Aired the entire first half of the final season in a half-day marathon, then played the final episodes late at night, with the Mask movie following it.
- Chowder - Probably the worst screwing yet, only 7 episodes were ordered for the last season, and when a new episode was announced, it was replaced by a rerun at the last minute
- The Marvelous Misadventures of Flapjack - Same as Chowder
- Transformers Animated - Was never advertised, toys were released in it's third season because Wal-Mart wanted Hasbro to make more toys based on the Transformers movie, and then cancelled it in order to make room for the polarizing second Transformers film.
- Robotomy - Was too expensive to produce, was never advertised, scheduled reruns were cancelled and replaced with other shows, and then after the last episode aired, CN removed all evidence that they ever aired the show.
- Sym-Bionic Titan - Yet another big insult, screwed with the shows timeslot, and was cancelled because "they couldn't get any companies to make toys for it because of 'a female lead character in what is considered to be a boys franchise'", (which is ridiculous since Young Justice has toys for it's female characters), creator Genndy Tartakovsky left Cartoon Network partially because of this
- Generator Rex - Killed right before it's last season ended, the last few episodes didn't even air
And for shows that are showing signs of being cancelled:
- Star Wars: The Clone Wars - Originally a network favorite, it's not that aired much anymore, and it's last aired episode ended on a cliffhanger
- Thundercats - While overall good ratings, a second season is in limbo, since CN "apparently couldn’t find a toyline", despite promises that the show was supposed to get 52 episodes (it has 26 so far, which is half that amount), ironic since I've seen toy advertisements for the 2011 series before, and have seen them at Wal-Mart.