I also love Hakoda/Bato and Roku/Sozin. Hakoda and Bato are two of my favorite characters and I love them together. I agree with Analeisa with "BFFs with benefits before they find their wives." But I see that with basically any two men who are really good friends. I guess I've read too many fanfics and enjoy them too much.
As for the younger characters, Jetko is probably my favorite. Jet is obsessively stalking Zuko all the time, so SOMETHING had to happen. I know Zuko does the same to Aang, but Aang seems to be too interested in Katara.
Slash ships are the best kind in fandom, to me. There are so many possibilities!