Although it is an anime/manga, tons of fanboys said Naruto jumped the shark when they brought back a lot of the main characters back to life when they died.
Fanboys also say Death Note jumped the shark when L was killed. I personally don't think the shows/mangas jumped the shark at those points, but I can see why people would think that.
That does remind me. I'd say One Piece Jumped the Shark in the Crocodile arc. Too many characters, way too slow. It only got worse from that point on.
Interesting, I haven't gotten that far in the series yet. I'll keep that in mind.
Law & Order: SVU has seem to have a few jumping the shark moments, but they never had really affected the show or hurt it in anyway. Those times usually happen when they lose or get rid of an ADA since the fan base is always annoyed and upset that the next person won't be good.
You seem to like anime more than I do, so you might be more tolerant of how slow the show starts to get (you'll have like 6 fights going on at once, and it'll take like an entire season to finish them all - and the leadup to the fight will be another season. No joke.). I will say it's more tolerable as a manga now, since the pacing is always faster in the manga than in the series. And both are still enjoyable, they've just gotten bogged down and aren't AS enjoyable.
Speaking of SVU.. The original Law & Order... I remember a lot of people saying the show was done when the original DA left. I think a bigger loss than that was Michael Moriarty, I liked his assistant DA more as a character than the current one. But, I don't think the show jumped at that point. I think it jumped when Jerry Orbach left/died. I think Lennie Briscoe is one of the greatest TV characters of my generation, and the loss of him killed my interest in the show. The quality had already slipped a bit by that point, but either it didn't bother me as much or it wasn't as bad before that point.