OK I'll take a crack at a few of them...
Samurai Champloo ~ I don't see the need to drag this story out any longer. I think the ending was very good, and I feel like adding to it will just water the series down.
Bamboo Blade ~ Will probably make another 24 episodes or so, bit it had cought up to the manga at the time, so I could see them making more if there is a want for it.
K-On - Slice of life. No matter how much we may love them. This one has no depth to it. It is over. Move on...
Shijō Saikyō no Deshi Kenichi (or histories strongest deciple) ~ last i hear they were thinking about making more. But I haven't looked into in it a long time. Definitely would be a good one to continue. I know they cought up witht he manga, but now the manga is up to 32, but it has only been a Taiwan release
Trigun ~ It was good, Ended good. Leave it be.
Toradora! ~ Another one where i feel if you add more to it, you water down it's greatness.
Kanokon ~ you are kidding me right. This one in no way deserves anymore than it has already given. I mean really, how much more do you want to see the guy get embarassed by a fox g-d? Well if you don
you are luckyGenshiken ~ they should finish out the Manga. It has a really good ending in my eyes. It would work well as a 6 series ova or they could push it to a 12 series season. Definitely worth another few episodes.
Seto no Hanayome ~ I liked the ending, didn't feel like a clifthanger to me.
Black Lagoon ~ They are making more. I think a few
movies or OVA's I don't recall which though.
Tenjou Tenge ~ would be really hard to make more, because the manga goes off into left field right as the series ends. Read the manga though and it will make you happy. I'd like to see more though. And it is a terrible hanger
On
Claymore ~ I'd like to see more. And even though i know they deviated from the manga. It was still a great watch!
F/S Night ~ Don't #$% with my F/S Night. The ending was great, and yes i have played the game and there are different endings. But you can't complain because they did an awesome job with the series up and down. Jump over to the
Fate/Stay Night forum and Havoc, Tatsu, XinWind, Asarta, a few others, and I will be more than happy to talk to you all about the series

Oh and
here is something to give you tingly feelings insideSo yeah... That's what I have to say on those series... IF you want deep explainations i'll give them to you, but those are my 2 cent answers. Can you aford the 2 dollar ones
