All of them.

Most shows on Cartoon Network, Nickelodeon & Disney Channel nowadays
Honey Boo Boo
2 Broke Girls
Chuck (after Season 2)

What really gets me is rubbish shows that did end/get cancelled yet are still repeatedly shown on tv! Teletubbies for example, i had to watched it 10 years ago first time round babysitting my neighbours daughter. Now ten years on having to watch it all over again on tv with my own kids.

Keeping up with the Kardashins ( however you spell their name)
Johnny Test (I just hate this show)
Most of the things on Cartoon Network and just bring back the classics like Ed, Edd, Eddy
Most of the things on MTV and just bring back the music, that's what MTV stands for

2 Broke Girls - Immediately
Two and a Half Men - After Sheen left
Scrubs - After the 8th season

The Simpsons...not many good episodes since season 10, although the movie was good
Pokemon
99% of reality shows
MTV should be about music, not reality shows
Cartoon Network should be ALL cartoons, hence the name XD

Real housewifes of wherever the hell they are. (Those shows make women look bad.)
Keeping up with the Cardassians (I wish that was the real show.)
Everythinjg on E! (or just cancel the network.)
Every 24 hour news network in the United States.

Spongebob

Ultimate Spider-Man!

I still cannot believe they cancelled Spectacular in favor of what is essentially an ad campaign for Joss Whedon's Marvel movieverse. It's got some of the cheapest writing and creative decisions I've ever seen. I can't believe Paul Dini actually is the creative consultant and a writer for it.

Reality TV also would do well to just die already.

A list of shows that should have been cancelled:
Glee
Glee
Glee

I'm forced to flick through up to six cooking shows a day sometimes! Not all at once, but since when has food become such a popular TV subject? I personally find them boring as shit, and I spend half of my shifts at work in a kitchen myself (not cooking, thank God) and based on what I see - being a chef ain't always glamorous work, or even fun to watch I guess my problem is not so much the fact they exist - but the fact there are so many clones of essentially the same concept

Same goes for all this antiquing stuff and rednecks wrestling down wild animals. They were original ideas for shows that were entertaining to watch - until every idiot who lives in central US (or Canada ) that has a video camera capturing their antics got some air time too for doing the exact same thing

And any reality show centering around some shallow bitch whose famous just for being famous in spite of having no actual talent

The Simpsons. Behind the Laughter was the last worthwhile episode.
Family Guy
Johnny Test
Every single reality show

Anything on Disney Channel save for the cartoons (even though I could care less for them).

Any live action shit on CartoonNetwork.

Johnny Test (why this was still left alive but Lazlo, Flapjack, Chowder, & Gym Partner's a Monkey were cancelled much before is beyond me).

Anything on Nickelodeon that came after iCarly.

Spongebob - As much as I loved this show, it died severely after that movie. I never thought the day would come that I wish this show would just end, unless they bring back the old crew.

Brickleberry.