If Osamu Adachi played Hunny, I'd be the happiest fangirl in the world. I'd be so happy I'd probably die.
My other Ouran choices:
Tamaki- I agree with [Salamandra], I think Hiro Mizushima would do really well as Tamaki. Not only is his French pretty good, he can also pull off flamboyant, flirtatious personalities well (as proven in Hana Kimi).
Kyouya- 
Tamaki Hiroshi (it's a really suckish picture, I apologize). I think he'd do really well as Kyouya. He got the "I'm better than all of you" cold personality down pat in Nodame. Plus I adore him.
Hikaru/Kaoru-
Ikuta Toma. Really, I can't think of anyone more perfect. Also, two Ikuta Tomas in one drama makes for lots of happy fangirls.
Haruhi-
Matsushima Hatsune. She's never done a role where she's had to dress like a boy, but I thought her character in Akihabara@Deep had kind of a Haruhi personality (if Haruhi was an otaku hacker girl). Plus, I think she's got lots of potential as an actress even though she hasn't been in much.
Mori- 
Tsumabuki Satoshi. His character in Long Love Letter kind of reminded me of Mori. In general he reminds me of Mori.
Nekozawa- 
Hosoda Yoshihiko. Partially I'd like to see him play Nekozawa because I think he's the awesomest obscure actor ever, but mainly it's because I think he'd be perfect. From what I've seen of his acting, he can pull off a variety of roles, ranging from complete and total psycho (he was the creepy deranged guy in Life), to absolute sweetheart. I think creepily sweet is right up his alley.