They're not very juicy but I want to know anyway. From reddit, which is normally terrible at dishing up behind the scenes gossip unless it's during an AMA:
I wrote for a primetime show where one of the actors was very difficult to work with so the creator of the show ended the season with that character's life in peril. He became very apologetic and tried to get his act together, so he was not written off.
However, the following season he was back to the same shenanigans leading to him being killed off after that season. He was not informed until his contract was not renewed.
It was most definitely not a fantastic way [to die]. In fact, they didn't even get a death scene. The next season started and it was revealed that character was dead.
I work in TV but mostly comedy so I don't have tons of experience with actors getting killed off. But one example I saw was insane. The actor HATED doing the show and wanted off- even though they were under contract. It got so ugly that the creators decided to kill this character off, but the actor wouldn't even come to work to shoot a death scene- so it happened mostly off screen. In a later season the actor regretted leaving and came back "miraculously". It was bonkers but the showrunner was awesome and rolled with it.
The first's commenter is denying every guess, which is basically every redditor naming Two & a Half Men. Apparently Charlie Sheen's character was never in peril the season earlier though.
The second one seems like it should be easy, but naturally nothing comes to mind.
There's more gossip about shows at the link but mostly the same stuff you get from entertainment sites. If you don't like reddit, don't bother.
Oh, almost forgot: there was a comment by someone named 'Ijustgotkilled' who said he just got killed off on Once Upon A Time but the episode hasn't aired yet. He sounded hilariously drunk and sad, but the comment has been completely wiped. Could be a fake, but he sounded rather broken up about it.