I always liked his character design and also is weird personality.
And let's not forget his disguises; These are the best things of his character.
Based on design and 'coolness' i'll go for Fon. Verde and Bermuda's arcobaleno design were pretty nice as well, but when it comes to design + coolness i have to go for Fon. I'm pretty sure there are many people out there who likes Reborn , but for me i don't really like him especially the parts when he tries to act cool ( it just doesn't give me the cool vibe)
His disguise in the early chapters is really cool
Reborn because he's the worlds greatest Hitman. And he showed why during the last arc he was a match for Brumuda and he wasn't even fighting back....Collonel's tack with his Rifle is intense too
My Top 3 would be
Top 3 for me:
1. Lal Mirch
Lal is most definitely the most kick-ass female in the series and she doesn't let anyone push her around. I also love her outfits and her bitchslaps are hilarious. xD
Colonnello may seem tough and almost, if not as, Spartan as Reborn, but he is also a sweetheart, especially when it comes to Lal. His loyalty is unmatched and true self is just very very smexy. ;D
Reborn is obvious. He's spartan and violent, but in end, he's always pushing Tsuna to do his best. Even though he secretive and dangerous, he's one of the most trustworthy characters out there. And he's also great comic relief at appropriate times.
My favorite Arcobaleno is Reborn, strong, smart and comic!
My fave has to be Collonello. It's not only that in the few times we got to see him firing his legendary sniper he was waaay too cool, but I really like how his character is developed into always getting out of his way to protect Lal Mirch and their undying love until the end.
I also believe that out of all the Acrobaleno (putting aside Reborn maybe) he is the one that has a better understanding that there is none to little hope in Checkerface's promises. The only reason he plays along with the whole thing is because of even the smallest hope Lal Mirch might been saved. At the Arcobalenos' meeting after Reborn meets Bermuda again his only care is to protect Lal.